Booster that utilizes energy output from a power supply unit

ABSTRACT

A booster circuit generates a boosted output by boosting a low voltage output supplied as a target to be boosted and feeds back a part of the boosted output, an output by the booster circuit itself, to the booster circuit as operation energy. An auxiliary booster circuit outputs start-up energy generated based on a low voltage output to the booster circuit as start-up energy that is necessary for starting up the booster circuit.

TECHNICAL FIELD

The present invention relates to a booster and more particularly to abooster that utilizes energy output from a fuel cell or a solar cell.

BACKGROUND ART

Studies on utilization of fuel cells and solar cells as a power supplyfor mobile devices have been in progress. The reason being that the fuelcells have high energy density per unit weight and hence a largecapacity, moreover, the solar cells are portable due to their lightweight and thin structure.

The fuel cells produce power from a chemical reaction between hydrogenand oxygen. The fuel cells are considered to produce clean energybecause they neither discharge noxious gases such as nitrogen oxides(NO_(x)) nor make any noise. The weight energy density of the fuelcells, one of the indicators that meter the performance of the cells issaid to be ten times as high as that of lithium ion cells. This meansthat a 5-hour-driving note-type personal computer can be used for 50hours by employing the fuel cells. Due to these advantageous, the fuelcells are expected to drastically enhance convenience of the mobiledevices.

The solar cells are clean energy sources free of noxious gases and noiseand have an advantage over secondary cells, such as lithium ion cellsand nickel-cadmium cells, that energy does not have to be supplemented.Therefore, the solar cells alone or in combination with fuel cells areexpected to be used more and more in mobile devices.

Solar cells having a size suitable for use in the mobile devices have alow output voltage of about 0.5 volt (V) for a single cell. A solidpolymer electrolyte fuel cell (PEFC) and a direct methanol fuel cell(DMFC), which are expected to be used in the mobile devices, each has alow output voltage for a single cell of 0.6 V to 0.7 V without loads andaround 0.3 V when rated output is produced. These output voltages aredetermined based on the principles of power generation by fuel cells andsolar cells. Single cells alone cannot produce output voltages higherthan the above-mentioned voltages.

Therefore, with single cell batteries alone, neither the electronicdevices can be operated nor the secondary batteries, such as anickel-cadmium battery and a lithium battery, can be charged. Thiscompels one to use, for example, a technique of serially connectingsingle cells to form a battery module to obtain a voltage necessary foroperating the electric/electronic devices or charging the secondarycells.

However, this technique has the following problems.

First, in the case of fuel cells, there is an increase in cost forproducing the fuel cells due to the structure for uniformly distributingfuel and oxygen (air) to all the cells. Moreover, an output currentproduced by the structure is limited to a current from a cell thatreceives a minimum supply of fuel and oxygen or to a current of a cellthat generates the least current due to an inappropriate mixing ratio ofthe fuel and oxygen. Therefore, a countermeasure is taken for uniformlydistributing fuel and so on, such as providing grooves in flow channelsfor fuel and oxygen in the fuel cell. However, this increases the costsince the grooves need to be provided with a coat of a material that canendure corrosion.

On the other hand, two problems arise in case of the fuel cells. Thefirst problem relates to the output power. Some of the single cells thatconstitute a solar cell module may be under shadow, which leads to adecrease in the output voltage of the solar cells. In particular, whenthe solar cell module is mounted on a mobile device, it can be difficultfor the entire solar cell module to receive light always. In addition,if a structure is adopted in which the entire solar cell module receiveslight always, it may not suit to the user's satisfaction.

The second problem relates to the cost. To connect single cells of asolar cell serially to constitute a solar cell module, it is essentialto add bypass diodes, and to take countermeasures for insulation ofwiring that connects a front surface of one solar cell to a rear surfaceof a neighboring solar cell and between the single cells of the solarcell. To increase the module packing factor of the solar cell, it isnecessary to shorten the wiring between the single cells of the solarcell or decrease interstices for intercellular insulation. This requiresthe cells to be arranged with high precision. The countermeasures forintercellular insulation and the requirement of high precision are someof the reason that increase the cost.

Conventional technologies aimed at solving the problems include solarcell devices that use a tandem-type solar cell providing a relativelyhigh output voltage of a little less than 2 V to avoid serial connectionand use a booster circuit to charge a secondary cell (see, for example,Patent Document 1).

Patent Document 1: Gazette of Japanese Patent No. 3,025,106 (forexample, page 3, reference numeral 5 in FIG. 1)

In the solar cell device described in Patent Document 1, a tandem-typesolar cell is used in which the output voltage of the solar cell isboosted by constructing the solar cell by a plurality of layers andconnecting the layers directly one to another. Since the tandem-typesolar cell provides an output voltage of a little less than 2 V, thesolar cell can boot a booster circuit with an oscillation circuit of acomplementary metal oxide semiconductor (CMOS) type having a minimumstart-up voltage of about 1.4 V.

The tandem-type solar cells are cheaper only in comparison with a solarcell in which single cells are serially connected. In other words, whencompared with ordinary single cell solar cells, there still remains aproblem of complexity in the production process, so that the productioncost cannot be reduced drastically and the cost of the solar cell is notreduced.

The solar cell device disclosed in Patent Document 1 is provided with abooster circuit and it is necessary to first boot the booster circuitbefore the solar cell device can be operated. A predetermined amount ofstart-up energy needs to be supplied from a power supply unit.Accordingly, when the energy in the power supply unit is empty orinsufficient, the booster circuit cannot be boot.

A first object of the present invention is to provide a booster thatprevents an increase in production cost due to use of a special electriccell and allows a reduction in cost by multipurpose application ofcells.

A second object of the present invention is to provide a booster havinga booster circuit that can be boot without a power supply unit.

DISCLOSURE OF THE INVENTION

According to an aspect of the present invention, a booster includes abooster circuit to which start-up energy necessary for starting up thebooster circuit and operation energy necessary for continuing anoperation of the booster circuit are supplied, wherein the boostercircuit generates a boosted output obtained by boosting an input voltageas a target to be boosted; and a power supply unit that supplies thestart-up energy and the operation energy to the booster circuit.

According to another aspect of the present invention, a booster includesa booster circuit to which either one of start-up energy necessary forstarting up the booster circuit and operation energy necessary forcontinuing an operation of the booster circuit is supplied, wherein thebooster circuit generates a boosted output obtained by boosting an inputvoltage as a target to be boosted; a power supply unit that supplies thestart-up energy; and a selector circuit that outputs either one of thestart-up energy and the operation energy to the booster circuit, whereinthe booster circuit outputs all or a part of the boosted output to theselector circuit as the operation energy.

In the booster according to the above aspects, the selector circuitincludes a first rectifier element connected to between the power supplyunit and the booster circuit; and a second rectifier element that isnormally connected in a direction in which all or a part of the boostedoutput is fed back to the booster circuit.

In the booster according to the above aspects, the booster includes anoutput controller circuit that is provided in a stage subsequent to thebooster circuit and performs output control to the boosted outputobtained from the booster circuit.

In the booster according to the above aspects, the booster includes aunit that controls an ability of boosting of the booster based on theoutput control by the output controller circuit.

In the above aspects, with a configuration that the booster circuit isdriven by a power supplying unit different from the first cell that is amain power source, a boosted voltage can be obtained in a highefficiency even when the output voltage of the main power source is alow voltage power, so that there is no need to use a plurality of cellsthat is connected in series as the main power source. Accordingly,instability of the output voltage can be eliminated and cost can bereduced.

Moreover, by supplying a power necessary for the start-up and operationof the booster circuit from a selected output selected by the rectifierout of the power generation voltage from the power supplying unit and apart of the boosted output, target to be boosted, obtained from a firstcell, or a selected output obtained using a rectifier element that hasequivalent rectifying characteristics (such as a part between the baseand emitter of a bipolar transistor), the boosting capability of thebooster circuit can be increased. Use of the output controller circuitallows the booster circuit to operate without being influenced by thecontrol output from the output controller circuit to obtain stablestart-up characteristics when starting up the booster circuit.

According to still another aspect of the present invention, a boosterincludes a booster circuit to which start-up energy necessary forstarting up the booster circuit and operation energy necessary forcontinuing an operation of the booster circuit are supplied, wherein thebooster circuit generates a boosted output obtained by boosting an inputvoltage as a target to be boosted; and a power supply unit that suppliesthe start-up energy to the booster circuit, wherein the booster circuitfeeds back all or a part of the boosted output as the operation energyto the booster circuit.

According to the above aspect, a low voltage output, target to beboosted, is supplied to the booster circuit and start-up energy from thepower generating unit is input to the booster circuit while operationenergy necessary for continuing the operation of the booster circuititself is fed back to the booster circuit by the booster circuit itself.Accordingly, a boosted output for operating, for example, a mobiledevice can be obtained by utilizing a low voltage output.

According to still another aspect of the present invention, a boosterincludes a booster circuit to which either one of start-up energynecessary for starting up the booster circuit and operation energynecessary for continuing an operation of the booster circuit issupplied, wherein the booster circuit generates a boosted outputobtained by boosting an input voltage as a target to be boosted; a powersupply unit that supplies the start-up energy; and a selector circuitthat outputs either one of the start-up energy and the operation energyto the booster circuit, wherein the booster circuit outputs all or apart of the boosted output to the selector circuit and the power supplyunit.

According to the above aspect, a low voltage output, target to beboosted, is supplied to the booster circuit, and the selector circuit,to which both the start-up energy and operation energy are input,outputs either one of the start-up energy and operation energy to thebooster circuit. Accordingly, the boosted output for operating, forexample, a mobile device can be obtained utilizing the energy of a lowvoltage output and efficient utilization of boosted output energy can berealized.

According to still another aspect of the present invention, a boosterincludes a booster circuit to which start-up energy necessary forstarting up the booster circuit and operation energy necessary forcontinuing an operation of the booster circuit are supplied, wherein thebooster circuit generates a boosted output by boosting an input voltage,a target to be boosted, and outputs the boosted output; and a storageelement that stores the boosted output and generates a constant voltageoutput, and feeds back the constant voltage output as the start-upenergy and the operation energy to the booster circuit.

According to the above aspect, a low voltage output, target to beboosted, is supplied to the booster circuit, and start-up energynecessary for the start-up of the booster circuit itself and operationenergy necessary for continuing the operation of the booster circuititself are output from the storage element to which the boosted outputis input. Accordingly, the boosted output for operating, for example, amobile device can be obtained utilizing the energy of a low voltageoutput, and efficient utilization of boosted output energy can berealized.

According to still another aspect of the present invention, a boosterincludes a booster circuit to which either start-up energy necessary forstart starting up the booster circuit or operation energy necessary forcontinuing an operation of the booster circuit is supplied, wherein thebooster circuit generates a boosted output by boosting an input voltage,a target to be boosted, and outputs the boosted output; and a storageelement that stores the boosted output input through a rectifier elementconnected in a forward direction between the booster circuit and thestorage element and generates a constant voltage output, and outputs thestart-up energy; and a selector circuit that outputs either the start-upenergy or the operation energy to the booster circuit.

According to the above aspect, a low voltage output, target to beboosted, is supplied to the booster circuit and the selector circuit, towhich both the start-up energy as an output of the storage element andthe operation energy as an output of the booster circuit are input,outputs either one of the start-up energy and operation energy to thebooster circuit. Accordingly, the boosted output for operating, forexample, a mobile device can be obtained by using the energy of a lowvoltage output, a load on the storage element can be reduced, and costefficient utilization of boosted output energy can be realized.

According to still another aspect of the present invention, a boosterincludes a booster circuit to which start-up energy necessary forstarting up the booster circuit and operation energy necessary forcontinuing an operation of the booster circuit are supplied, wherein thebooster circuit generates a boosted output obtained by boosting an inputvoltage, target to be boosted; a power supplying unit that supplies thestart-up energy; a switching unit that performs output control of thestart-up energy, wherein the booster circuit feeds back all or a part ofthe boosted output to the booster circuit as the operation energy andoutputs the boosted output to the switching unit as a supply stop signalfor the start-up energy, and the switching unit performs control whetherto output the start-up energy to the booster circuit based on a start-upsignal based on power generation control of a low voltage output inputas the target to be boosted and the supply stop signal.

According to the above aspect, a low voltage output, target to beboosted, is input to the booster circuit, and the selector circuit, towhich both the start-up energy and the operation energy as an output ofthe booster circuit are input through the switching unit that operatesbased on the start-up signal output from the detecting unit, outputseither one of the start-up energy and operation energy to the boostercircuit. Accordingly, the boosted output for operating, for example, amobile device can be obtained by using the energy of a low voltageoutput, and the start-up energy can be output only when it is necessaryto start up the booster circuit, so that it is possible to use thestart-up energy efficiently.

According to still another aspect of the present invention, a boosterincludes a booster circuit to which either one of start-up energynecessary for starting up the booster circuit and operation energynecessary for continuing an operation of the booster circuit issupplied, wherein the booster circuit generates a boosted outputobtained by boosting an input voltage as a target to be boosted; a powersupplying unit that supplies the start-up energy; a switching unit thatperforms output control of the start-up energy; and a selector circuitthat outputs either one of the start-up energy and the operation energyto the booster circuit, wherein the booster circuit outputs all or apart of the boosted output to the selector circuit and the powersupplying unit, the switching unit performs control whether to outputthe start-up energy to the selector circuit based on a start-up signalbased on power generation control of a low voltage output input as thetarget to be boosted.

According to the above aspect, a low voltage output, target to beboosted, is input to the booster circuit and the selector circuit, towhich both the start-up energy and the operation energy as an ouptput ofthe booster circuit are input through the switching unit that operatesbased on the start-up signal output, outputs either one of the start-upenergy and operation energy to the booster circuit. Accordingly, theboosted output for operating, for example, a mobile device can beobtained by using the energy of a low voltage output, and the start-upenergy can be output only when it is necessary to start up the boostercircuit, so that it is possible to use the start-up energy efficiently.All or a part of the boosted output is output and stored in the powersupplying unit, so that the consumed start-up energy can be effectivelysupplemented.

According to still another aspect of the present invention, a boosterincludes a booster circuit to which either one of start-up energynecessary for starting up the booster circuit and operation energynecessary for continuing an operation of the booster circuit issupplied, wherein the booster circuit generates a boosted outputobtained by boosting an input voltage as a target to be boosted; a powersupplying unit that supplies the start-up energy; a switching unit thatperforms output control of the start-up energy; a selector circuit thatoutputs either one of the start-up energy and the operation energy tothe booster circuit; and a signal delay circuit that generates a delaysignal obtained by delaying a power generation request signal sent forpower generation control of a low voltage output input as the target tobe boosted by a predetermined time and outputs the delay signal, whereinthe booster circuit outputs all or a part of the boosted output to theselector circuit and the power supplying unit, and the switching unitperforms control whether to output the operation energy to the selectorcircuit based on the delay signal.

According to the above aspect, a low voltage output, target to beboosted, is input to the booster circuit and the selector circuit, towhich both the start-up energy and the operation energy as an output ofthe booster circuit are input through the switching unit that operatesbased on the start-up signal output, outputs either one of the start-upenergy and the operation energy to the booster circuit. Accordingly, theboosted output for operating, for example, a mobile device can beobtained by using the energy of a low voltage output, and the start-upenergy can be output only when it is necessary to start up the boostercircuit, so that it is possible to use the start-up energy efficiently.All or a part of the boosted output is output and stored in the powersupplying unit, so that the consumed start-up energy can be effectivelysupplemented.

According to still another aspect of the present invention, a boosterincludes a booster circuit to which either one of start-up energynecessary for starting up the booster circuit and operation energynecessary for continuing an operation of the booster circuit issupplied, wherein the booster circuit generates a boosted outputobtained by boosting an input voltage as a target to be boosted; and anauxiliary booster circuit that outputs the start-up energy generatedbased on the low voltage output to the booster circuit, wherein thebooster circuit feeds back all or a part of the boosted output to thebooster circuit itself as the operation energy.

According to the above aspect, the booster circuit, which is started upby the auxiliary booster circuit that outputs start-up energy generatedbased on a low voltage output to the booster circuit, feeds back a partof the boosted output that is output by the booster circuit itself tothe booster circuit itself as operation energy. Accordingly, the boostercircuit itself can be started up or continue the boosting operation ofthe booster circuit itself independently of the power supplying unitother than the power generating element that outputs a low voltageoutput, so that boosting of the power generation energy output from thepower generating element can be performed reliably.

According to the above aspects, the first object of the presentinvention that is to provide a booster that prevents an increase inproduction cost due to use of a special electric cell and to allow areduction in cost by multipurpose application of cells can be achieved.

Moreover, the second object of the present invention to provide abooster that can start up a booster circuit independently of start-upenergy from a power supply unit can be achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a configuration of a booster according to afirst embodiment of the present invention;

FIG. 2 is a block diagram of a configuration of a booster according to asecond embodiment of the present invention;

FIG. 3 is a diagram of a configuration of a booster circuit for boostingan output of a solar cell having a construction of a boost converteraccording to a first example of the present invention;

FIG. 4 is a diagram of a configuration of a booster circuit for boostingan output of a solar cell having a construction of a boost converteraccording to a second example of the present invention;

FIG. 5 is a block diagram of a configuration of a booster according to athird embodiment of the present invention;

FIG. 6 is a block diagram of a configuration of a booster according to afourth embodiment of the present invention;

FIG. 7 is a diagram of a configuration of a booster circuit for boostingan output of a solar cell according to a third example of the presentinvention;

FIG. 8 is a diagram of a configuration of a booster circuit for boostingan output of a solar cell that has a construction of a boost converterwith an output control function and that is not serially connectedaccording to a fourth example of the present invention;

FIG. 9 is a block diagram of a configuration of a booster according to afifth embodiment of the present invention;

FIG. 10 is a block diagram of a configuration of a booster according toa sixth embodiment of the present invention;

FIG. 11 is a block diagram of a configuration of a booster according toa seventh embodiment of the present invention;

FIG. 12 is a block diagram of a configuration of a booster according toan eighth embodiment of the present invention;

FIG. 13 is a block diagram of a configuration of a booster according toa ninth embodiment of the present invention;

FIG. 14 is a block diagram of a configuration of a booster according toa tenth embodiment of the present invention;

FIG. 15 is a block diagram of a case where a switching unit 27 isconstituted by switching elements 51 a and 51 b that are seriallyconnected one to another;

FIG. 16 is a block diagram of a configuration of a booster according toan eleventh embodiment of the present invention;

FIG. 17 is a block diagram of a configuration of a booster according toa twelfth embodiment of the present invention;

FIG. 18 is a block diagram of a configuration of a booster according toa thirteenth embodiment of the present invention;

FIG. 19 is a schematic for explaining a principle of operation of aswitched capacitor type;

FIG. 20 is a schematic for explaining a circuit configuration and aprinciple of operation of a charge pump type;

FIG. 21 is a diagram of a configuration of a booster according to afourteenth embodiment of the present invention;

FIG. 22 is a diagram of a configuration of a booster according to afifteenth embodiment of the present invention;

FIG. 23 is a diagram of one example of a configuration of an outputcontroller circuit 16 a;

FIG. 24 is a diagram of another example of the configuration of theoutput controller circuit 16 a;

FIG. 25 is a diagram of a configuration of a booster according to asixteenth embodiment of the present invention;

FIG. 26 is a diagram of one example of a configuration of an outputcontroller circuit 16 b;

FIG. 27 is a diagram of a configuration of a booster according to aseventeenth embodiment of the present invention;

FIG. 28 is a diagram of a configuration of a booster according to aneighteenth embodiment of the present invention;

FIG. 29 is a diagram of a configuration of a booster according to anineteenth embodiment of the present invention; and

FIG. 30 is a diagram of a configuration of a booster according to atwentieth embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Exemplary embodiments of a booster according to the present inventionare explained in detail with reference to the accompanying drawings. Thepresent invention should not be considered as being limited by theembodiments.

First Embodiment

FIG. 1 is a block diagram of a configuration of a booster according to afirst embodiment of the present invention.

The booster for an output of a solar cell shown in FIG. 1 is applicableto an output of a solar cell 11, which is not a constituent element ofthe booster of the present invention, as a target to be boosted. Thebooster includes a solar cell 14 and a booster circuit 12 as a powersupply unit, and supplies power to a load (secondary cell) 19.

When light falls on the solar cell 11, which is not serially connected,as a target to be boosted, electromotive force occurs. Typicalwidespread solar cells made of monocrystalline silicon, polycrystallinesilicon, amorphous silicon, and compound semiconductors can be used asthe solar cell 11. The single cells of these solar cells have an outputvoltage of at maximum a little higher than 0.5 V. The power generated bythe solar cell 11 is boosted by the booster circuit 12 and then suppliedto the load (secondary cell) 19. The load (secondary cell) 19 is anyelectric or electronic circuit. The booster circuit 12 does not operateat a voltage of below 0.6 V, so that the booster circuit 12 cannot bedriven with only the solar cell 11. The booster circuit 12 is configuredto receive a power supply from the solar cell 14, which includesserially connected single cells of an amorphous solar cell or a solarcell that can be manufactured at a cost as low as the cost of theamorphous solar cell. The area of the solar cell 14 only needs to be ofa size that is large enough to generate the power required to operatethe booster circuit 12. In other words, small elements of area of about1 cm³ to about 3.3 cm³ can be used as the solar cell 14.

The serially connected amorphous solar cell 14 can be advantageouslyused as a power source for the booster circuit 12. Amorphous solar cellshave a feature that they can be serially connected in the semiconductorprocesses and do not have the various problems that generally occur inthe conventional technologies.

The booster circuit 12 that has a boost type circuit configuration isuseful. A metal oxide semiconductor field effect transistor (MOSFET)that has a feature that it requires an extremely low driving power isused as a switching element in the booster circuit 12. Moreover, amultivibrator oscillator circuit with a complementary metal oxidesemiconductor (CMOS) logic integrated circuit (IC) is used for a drivingunit of the MOSFET. An oscillation frequency of the multivibrator isdetermined based on the power consumed by the oscillator circuit, and aninductance and rated current of a coil of a booster converter. Theoscillation frequency of the multivibrator and the inductance and ratedcurrent of the coil of the boost converter are factors of design thatare determined by the capability of the power generation of the solarcell 11, a target to be boosted, and are known technologies, so thattheir explanation will be omitted.

The booster circuit 12 configured from requisite minimum componentsconsumes extremely low power and can operate at a power of 10 microwatts(μW) or less when operating at 10 kilo Hertz (kHz). A minimum voltage ofstart-up and operating voltages of a booster circuit that includes aCMOS logic IC 74HC14 as a multivibrator circuit is 1.2 V. When the solarcell 14 used is an amorphous solar cell that includes therein five cellsof a size of 33 millimeters (mm)×10 mm serially connected, boostingoperation was confirmed at a luminance of about 1,100 luxes or more.

If a large size MOSFET or a plurality of MOSFETs are used as a switchingelement with the object of increasing the boosting capability of thebooster, the power consumed by the booster circuit 12 increases, therebyincreasing a minimum luminance at which the booster circuit 12 startsup.

In this embodiment, the solar cell 11, which is the first cell, is asingle-cell solar cell that is of a low-power-outputting type and can beproduced without complicated production processes such as configuratinga serial connection. However, a single-cell fuel cell that is alow-power-outputting type and can be configured without serialconnections can be used instead. Also, when the object is to increase anoutput to the boosting circuit 12, parallelly connected fuel cells orsolar cells that can be realized without passing complicated productionprocesses can be used.

On the other hand, the solar cell 14, which is the second cell, whichplays a role of an energy source that provides start-up energy(operation energy), may be any solar cell that can supply energy. Forexample, a lithium storage cell may be used. The solar cell 14 may be aprimary cell, which cannot be charged, such as a dry cell, or a storageelement such as an ordinary capacitor or an electric double-layercapacitor.

Second Embodiment

FIG. 2 is a block diagram of a configuration of a booster according to asecond embodiment of the present invention.

The booster circuit has a configuration that realizes an increase in theboosting capability of the booster circuit without causing an increasein minimum luminance for starting up the booster circuit. Theconfiguration shown in FIG. 2 includes a selector circuit 15 in theconfiguration shown in FIG. 1 according to the first embodiment. Theselector circuit 15 that two rectifier elements 32 and 33.

The booster circuit 12 uses a power from the solar cell 14 when startingup. Moreover, after a boosting operation is started, the booster circuit12 uses a part of the boosted power thereby drastically increasing theboosting capability of the booster. Since the power of the solar cell 14and a part of the boosted power is selectively supplied to the boostercircuit 12, the power of the solar cell 14 is supplied only to thebooster circuit 12 but not to the load (secondary cell) 19, a decreasein start-up luminance can be prevented. The booster circuit 12 starts upwhen it receives a supply of power from the solar cell 14, and thebooster circuit 12 supplies a power from the boosted power to thebooster circuit 12 through the rectifier element 33 when boostingoperation has started. As a result, the boosting capability of thebooster circuit 12 increases. The more the power generated by the solarcell 11 increases, the more the boosted power increases, thus increasingthe power supplied to the booster circuit 12 through the rectifierelement 33. As a result, the boosting capability of the booster circuit12 is augmented to create a virtuous cycle. Note that a rectifierelement that has equivalent rectifying characteristics (such as aportion between the base and emitter of a bipolar transistor) may beused instead of the rectifier elements 32 and 33. The details of thecircuit configuration of the booster circuit are explained below usingexamples.

In the second embodiment, the solar cell 11, which is the first cell, isa single-cell solar cell that is of a low power outputting type and canbe produced without complicated production processes such asconfigurating a serial connection. However, a single-cell fuel cell thatalso is of a low power outputting type and can be configured withoutserial connection may be used. Also, when it is desired to increase anoutput to the boosting circuit 12, parallelly connected fuel cells orsolar cells that can be realized without passing complicated productionprocesses may be used.

The solar cell 14, which is the second cell, which plays a role of anenergy source that provides start-up energy (operation energy), may beany solar cell that can supply energy. For example, a lithium storagecell may be used. In addition, the solar cell 14 may be a primary cell,which cannot be charged, such as a dry cell, or a storage element suchas an ordinary capacitor or an electric double layer capacitor.

Examples of the present invention is explained with reference to theaccompanying drawings.

FIRST EXAMPLE

In a first example, a booster circuit of a boost converter configurationis explained.

FIG. 3 is a diagram of a configuration of a booster circuit of a solarcell having a configuration of a boost converter according to the firstexample of the present invention.

A target to be boosted by a booster circuit 202 is a solar cell 201 thatis not serially connected. The booster circuit 202 has an outputterminal 217, to which an electronic load (Fujitsu Denso, EULαXL150)that can be controlled to a constant current and constant voltage isconnected as a load 203. The solar cell 201 used is a36-square-centimeter (cm²) silicon polycrystal that generates an openend output voltage at AM1.5 of 0.56 V. The booster circuit 202 usedincludes a coil 206 that has a direct current resistance of 20milliohms, a rated current of 2 amperes (A), and an inductance value of22 microhenries. A switching element 208 used includes Si9948DYmanufactured by Siliconix as a MOSFET. A diode 207 used is a Schottkybarrier diode CMS06 manufactured by Toshiba Corporation. A capacitor 209used is an electrolytic capacitor manufactured by Sanyo having anelectron spin resonance (ESR) of 20 milliohms and a capacitance of 220microfarads. An oscillator circuit 224 includes a multivibratoroscillator circuit by means of a Schmitt trigger type inverter 74HC14,which is a versatile CMOS logic gate and a driver circuit for augmentingan output current.

The multivibrator circuit includes a capacitor 210 that determinesoscillation time constant, a resistor 211, and a Schmitt trigger typeinverter 213. However, here, a general low power consuming typerectangular wave oscillator circuit can be used.

The driver circuit used includes Schmitt trigger type inverters 212 and214 connected in parallel. A general low power consuming type inverteror a buffer type logic gate can also be used. The number of parallelgates may be determined depending on the current driving capability andload. Since a supply of power to a power source terminal 215 of theSchmitt trigger type inverter 74HC14 in the oscillator circuit 224 isnecessary as a power source of the booster circuit 202, the seriallyconnected solar cell 204 and a capacitor 216 are connected to the powersource terminal 15. As the solar cell 204, an amorphous solar cell of a5-cell configuration manufactured by Sanyo, having a rated output of 3.0V and 2.2 mA, and a model number of AM1156 is used. The capacitor 216used is an OS electrolytic capacitor of 220 microfarads manufactured bySanyo. The solar cell 201 and the solar cell 204 are arranged close toeach other on a plane.

Measurement of luminance is performed using an illuminometer 510-02manufactured by Yokogawa Electric Corporation in such a manner that adistance from a light source and a surface of a solar cell is madeequivalent to a distance from the light source and a light-receivingbulb of the illuminometer.

Experimental results indicate that boosting operation started at 1,100luxes. Adjustment of the oscillation frequency of the oscillator circuit224 varied a boosting start voltage and the boosting start voltage wasmost sensitive at an oscillation frequency of about 1 kHz to about 30kHz. It has been demonstrated that when the output voltage of the solarcell 204 used as a driving source of the booster circuit exceeds 1.1 V,the oscillator circuit 224 starts oscillation but the switching element208 is not driven whereas when the output voltage of the solar cell 204exceeds 1.4 V, the boosting operation starts. When the illuminance was1,100 luxes, the output voltage of the solar cell 204 reached 1.4 V.Although sufficient boosting operation is obtained near a window orunder sunlight and a voltage of 20 V or more is obtained at the outputterminal 217, the solar cell 204 provides an output voltage of about 1.9V but does not reach rated voltage of 3.0 V. Therefore, augmentation ofthe supply of energy to the booster circuit after the start-up of thebooster circuit was performed.

Note that the 74HC14 is a standard package that includes six inverterlogics and power source supply terminals to the logics all together. Theoscillator circuit 224 is configured by using the three inverter logics21, 213, and 214 of 74HC14 and the resistor 211 and the capacitor 210.

SECOND EXAMPLE

In a second example, a booster circuit of a boost converterconfiguration that is different from the booster circuit in the firstexample is explained.

FIG. 4 is a diagram of a configuration of a booster circuit of a solarcell having a configuration of a boost converter according to the secondexample of the present invention.

The output from the solar cell 204 and the boosted output from thebooster circuit are applied to the power source terminal 215 of theSchmitt trigger type inverter 74HC14 through an OR circuit formed by aSchottky diode 218 and a Schottky diode 219.

The output of the solar cell 204 is supplied to the booster circuit 202only but not to the load 203 because of the diode 219, so that thestart-up illuminance is not deteriorated as compared with that of thefirst example.

In experiments, irradiation of light at 1,200 luxes or more caused thebooster circuit to start, and a boosted output was obtained from thesolar cell 201. The boosted output is supplied to the load 203. At thesame time, a part of the output is supplied to the booster circuit 202through a current limiting resistor 220 and the diode 219. That is, theboosted output is supplied to the power source terminal 215 of theSchmitt trigger type inverter 74HC14 that constitutes the oscillatorcircuit. When the supply of the energy from the boosted output to thebooster circuit 202 is started, the voltage of the power source terminal215 of 74HC14 increases to stabilize the operation of the oscillatorcircuit 224 and start driving the switching element 208 and a switchingelement 221 with sufficient driving capability, so that ON resistancesof the switching elements 208 and 221 can be decreased. In theexperiments where Si9948DY was used for the switching elements 208 and221, a combined value of ON-resistances obtained was 10 milliohms.

This means that when the coil 206 has a direct current of 20 milliohms,the direct current resistance of the booster circuit reaches about 30milliohms, so that a generated current of at most 10 A can be introducedfrom the solar cell 201 into the booster circuit 202 when the solar cell201 provides a power generation voltage of 0.3 V.

In the booster circuit of this example, once the booster circuit 202 isstarted, a part of the boosted output is supplied to the booster circuit202, so that the solar cell 204 used for the start-up is no longernecessary.

Since irradiation of light of about 5,000 luxes produces a boosted powerof above 7V, an electric load EULαX150 manufactured by Fujitsu Denso wasconnected to the load 203 and a constant operation was set.

Table 1 below shows one example of results obtained when an outputvoltage Vin of the solar cell 201 not serially connected, target to beboosted, was varied at various luminances.

TABLE 1 Vin Iin Win Vout Iout Wout Efficiency (V) (mA) (mW) (V) (mA)(mW) (%) 0.50 330 165 5.002 27 135 81.9 0.40 280 112 5.002 19.1 95.585.0 0.30 210 63 5.002 9.7 48.5 77.0 0.20 150 30 5.002 4.7 23.5 78.40.10 110 11 5.002 1.9 9.5 86.4

In the experiments, the electric load used as the load 203 was set at5.00 V for a constant voltage operation. A boosted output was calculatedfrom an output voltage and an output current at the output terminal 217of the booster circuit that were measured. The results indicated thateven when the output voltage of the solar cell 201 was 0.1 V, a boostedoutput was obtained and a high conversion efficiency on the order of 80%was obtained. The rectangular wave oscillator circuit including amultivibrator used in the experiments was not configured so as to varythe duty ratio, so that for example, when the output voltage Vin of thesolar cell 201 was 0.5 V, the supply current Iin from the solar cell 201was 330 milliamperes (mA). However, the duty ratio can be controlled.Experiments using a separate rectangular wave oscillator circuitindicated that an increased duty ratio enabled the booster circuit 202to incorporate the output current lin from the solar cell 201 even whenthe output current lin exceeds 1,500 mA. The 74HC14 is a standardpackage that includes six inverter logics and power source supplyterminals to the logics all together. The oscillator circuit includesthe three inverter logics 212, 213, and 214, the resistor 211, and thecapacitor 210.

Third Embodiment

FIG. 5 is a block diagram of a configuration of a booster according to athird embodiment of the present invention.

The configuration of a booster for an output from a solar cell with anoutput controller circuit corresponds to the configuration of thebooster shown in FIG. 2 according to the second embodiment whichincludes an output controller circuit 16.

The electric power generated by the solar cell 11, a target to beboosted, is boosted by the booster circuit 12 and subjected to outputcontrol for a constant voltage or constant current or for charging, andthen supplied to an electric or electronic circuit or the load(secondary cell) 19, which is a secondary cell through a rectifierelement 34. A part of the boosted power is supplied to the outputcontroller circuit 16 and the booster circuit 12. The power of the solarcell 14 for starting up the booster circuit 12 is supplied to thebooster circuit only by the action of the rectifier element 33, so thata decrease in the start-up luminance can be prevented. Since currentdoes not flow back in the direction of the load (secondary cell) 19 tothe output controller circuit 16 because of the rectifier element 34,unnecessary discharge of the secondary cell can be prevented when asecondary cell is used as the load (secondary cell) 19. When the load(secondary cell) 19 is not a secondary cell, the rectifier element 34may be omitted. The output controller circuit 16 to be used may beeither a 3-terminal series regulator or a simple configuration in whicha constant voltage diode is used. The details of the circuitconfiguration of the booster circuit are explained in exampleshereinbelow.

In this embodiment, the solar cell 11, which is the first cell, is asingle-cell solar cell that is of a low power outputting type and can beproduced without complicated production processes such as configuratinga serial connection. However, a single-cell fuel cell that also is of alow power outputting type and can be configured without serialconnection may be used. Also, when it is desired to increase an outputto the boosting circuit 12, parallelly connected fuel cells or solarcells that can be realized without passing complicated productionprocesses may be used.

The solar cell 14, which is the second cell, which plays a role of anenergy source that provides start-up energy (operation energy), may beany solar cell that can supply energy. For example, a lithium storagecell may be used. In addition, the solar cell 14 may be a primary cell,which cannot be charged, such as a dry cell, or a storage element suchas an ordinary capacitor or an electric double layer capacitor.

Fourth Embodiment

FIG. 6 is a block diagram of a configuration of a booster according to afourth embodiment of the present invention. The booster has aconfiguration of a booster for an output from a solar cell, aimed atmaking the boosting capability of the booster variable. Also, FIG. 6 isintended to explain the configuration of the booster circuit shown inFIG. 5 according to the third embodiment in which a control signal issent from the output controller circuit 16 to the booster circuit 12 tomake the boosting capability of the booster variable, thereby achievingcontrol of the target.

The booster for an output of a solar cell shown in FIG. 6 starts up whenreceiving a power from the solar cell 14 at the time of start-up of thebooster circuit 12. Since in this point in time, neither a boostedoutput is generated nor the boosted output reaches a minimum operationvoltage of the controller circuit 16, there exists no control signalfrom the output controller circuit 16 or the output controller circuit16 operates unstably. For this reason, the booster circuit that hasstarted up in an undesirable signal state stops, so that there is a fearthat normal operation will not be performed. To solve this problem, itis necessary that a circuit configuration having the followingcharacteristics be adopted.

-   -   (1) At the time of start-up, no unstable control output must be        provided from the output controller circuit 16 to the booster        circuit 12.    -   (2) At the time of start-up, a control signal output terminal of        the output controller circuit 16 must be at a high impedance.

To prevent the output controller circuit 16 from outputting unstablecontrol signals, it is effective that a current driving element such asa bipolar transistor be used in a control signal outputting stage. Thecurrent driving element needs current for turning the element ON, andwhen starting up the booster circuit, the output controller circuit doesnot have sufficient capability for driving the current driving element.Setting the output terminal at a high impedance allows current to flowfrom the booster circuit 12 to the output controller circuit 16, so thatdeterioration of the start-up characteristics of the booster circuit canbe prevented. Therefore, it is effective that a configuration of an opendrain or an open collector by using parallelly connected resistorsbetween the gate and source to form a current driving type be used inthe control signal output stage of the output controller circuit 16. Thedetails of the circuit configuration of the booster are explained in theexamples hereinbelow.

The solar cell 11, which is the first cell, is a single-cell solar cellthat is of a low power outputting type and can be produced withoutcomplicated production processes such as configurating a serialconnection. However, a single-cell fuel cell that also is of a low poweroutputting type and can be configured without serial connection may beused. Also, when it is desired to increase an output to the boostingcircuit 12, parallelly connected fuel cells or solar cells that can berealized without passing complicated production processes may be used.

The solar cell 14, which is the second cell, which plays a role of anenergy source that provides start-up energy (operation energy), may beany solar cell that can supply energy. For example, a lithium storagecell may be used. The solar cell 14 may be a primary cell, which cannotbe charged, such as a dry cell, or a storage element such as an ordinarycapacitor or an electric double layer capacitor.

THIRD EXAMPLE

In a third example, a booster circuit of a boost converter configurationthat has an output-controlling function is explained.

FIG. 7 is a diagram of a configuration of a booster circuit for anoutput of a solar cell according to the third example of the presentinvention.

A rectangular wave oscillator circuit in a booster circuit 244 includesa multivibrator oscillator circuit by means of a Schmitt trigger typetwo-input inverter NAND (74HC132), which is a versatile CMOS logic gate,and a driver circuit for augmenting an output current. The multivibratorcircuit includes a capacitor 233 that determines an oscillation timeconstant, a resistor 232, and a Schmitt trigger type two-input NAND gate234. A low power consumption type rectangular wave oscillator circuitthat can be controlled of an oscillation state from outside theoscillator circuit may be used. The driver circuit used includes Schmitttrigger type two-input NANDs 235 and 236, and 237 connected in parallel.Here, a logic gate of a general low power consuming type inverter havingan excellent capability of driving current can be advantageously used.The number of parallel gates may be determined depending on the load.Since a supply of power to a power source terminal 230 of the Schmitttrigger type two-input NAND 74HC132 in the oscillator circuit 224 isnecessary as a power source of the booster circuit 244, the seriallyconnected solar cell 204 is connected to the power source terminal 230through the diode 218. As the solar cell 204, an amorphous solar cell ofa 5-cell configuration manufactured by Sanyo, having a rated output of3.0 V and 2.2 mA, and a model number of AM1156 is used. The capacitor216 used is a low ESR type electrolytic capacitor of 220 microfaradsmanufactured by Sanyo. In the same manner as that in the Example 2, theoutput of power generation of the solar cell 204 and the boosted outputfrom the booster circuit 244 are connected to the power source terminal230 in a configuration of OR by means of the diodes 218 and 219.

With this configuration, the output of power generation by the solarcell 204 can be supplied to the power source terminal 230 only and apart of the boosted output can be supplied to the power source terminal230 without flowing back from the boosted output to the solar cell 204.When a part of the boosted output is output to the power source terminal230, insertion of the current limiting resistor 220 can prevent a supplyof excessive power to the power source terminal 230, thereby increasingthe conversion efficiency of the booster circuit.

The diodes 218, 219, 207, and 238 are advantageously Schottky barrierdiodes that have characteristics of low potential drops in the forwarddirection. In this example, CMS06 manufactured by Toshiba Corporation isused.

Now, the output controller circuit is explained.

The third example is an example of a circuit configuration for making aboosted output at a constant voltage when an output from a non-seriallyconnected solar cell is boosted by the booster circuit 244. It is notessential for this booster circuit whether the boosted output iscontrolled to a constant voltage or a constant current and any knownoutput-controlling technologies can be used. What is needed is where toobtain a power that is required by the output controller circuit and howto interface control signals. The output voltage of the solar cell 201as a target to be boosted is about 0.4 V, at most a little higher than0.5 V. It is impossible to drive a comparator or a standard voltagesource that constitute a general output controller circuit at such a lowvoltage. The solar cell 204, another energy source, is to provide energynecessary for the start-up operation of the booster circuit 244 and itis assumed that a small area solar cell is utilized.

Diverting energy from the solar cell 204 could cause a decrease inoutput voltage of the solar cell 204, resulting in a considerabledecrease in the characteristics of low luminance operation of thebooster circuit of the present invention or a failure of starting up ofthe booster circuit 244. The output controller circuit needs to functiononly when the booster circuit 244 generates a boosted output. Therefore,known output-controlling units can be used without deteriorating thecharacteristics of low luminance operation of the booster circuit of thepresent invention by connecting the output controller circuit in such amanner that a voltage is obtained from the boosted output of thenon-serially connected solar cell 201 as shown in FIG. 7.

Then, an interfacing method of control signals is explained. Outputcontrols such as a constant voltage control and a constant currentcontrol can be realized by affecting the boosting operation of thebooster circuit 244 to control the boosting capability thereof. When theoutput control unit operates by obtaining a power from the boostedoutput from the booster circuit 244, the output control unit cannotoperate until a boosted output is obtained from the booster circuit 244.When the oscillator circuit in the booster circuit receives anoscillation permission signal that is not 0 (zero) volt to oscillate andcontrols the boosting operation, the following problems arise.

The booster circuit 244 starts oscillation and performs boostingoperation when an oscillation control terminal 260 receives anoscillation permission signal that corresponds to a high level of alogic. When the booster circuit 244 starts up, a boosted output is notgenerated yet, so that no oscillation permission signals are obtainedfrom the output-controlling unit, resulting in that the oscillatorcircuit cannot oscillate. Accordingly, the oscillation control terminal260 is connected to the power source terminal 230 through an integratorcircuit that includes a resistor 231 and a capacitor 245, as shown inFIG. 7. To increase an impedance of the output terminal of the outputcontroller circuit at a time other than outputting an oscillationpermission signal, the output terminal of control signals is designed tobe of an open drain configuration or an open collector configuration. Inthis circuit configuration, the voltage of the oscillation controlterminal 260 at the time of start-up is substantially equal to the powersource voltage of the power source terminal 230, so that the boostercircuit has characteristics that logic high can be stably obtained.

There are no power consuming factors that deteriorate the low luminancecharacteristics of the booster circuit of the present invention. As anoutput-controlling method for a booster for an output from a solar cellthat is not serially connected to solve the problems, an example of aconstant voltage output control is shown in the third example, and aconstant voltage control operation is explained.

The constant voltage controller circuit includes a comparator 241 of anopen drain output configuration, a standard voltage source 242, a biasresistor 239, and output voltage resistors 240 and 243 for setting anoutput voltage value, and the components are connected to each other asshown in FIG. 7. The comparator 241, which may be of an open drainoutput configuration or an open collector configuration, or of aconfiguration other than these, can be connected to the oscillationcontrol terminal 260 at the comparator output terminal through an N-typeMOSFET or NPN-type bipolar transistor.

Then, the operation of the booster is explained.

When the booster is started up by irradiation of sunlight, no boostedoutput is obtained, so that the N-type MOSFET or NPN transistor in theoutput stage of the comparator 241 is in a state of OFF, the voltage ofthe oscillation control terminal 260 increases, and the multivibrator inthe booster circuit starts oscillation to provide a boosted output. Whendivided voltages of the boosted voltage by 0-division resistors 240 and243 are higher than the voltage of the standard voltage source 242, theoutput of the comparator draws current, so that the oscillator controlterminal 260 is at a logic low, resulting in that the oscillation stopsand the boosting operation stops. When the output voltage is equal to orlower than values set by the divided resistors 240 and 243, the opendrain output circuit of the comparator turns OFF, the voltage of theoscillation control terminal 260 increases through an integrator circuitand the logic becomes a high level and then the booster circuit 244starts again oscillation to perform boosting operation to control theoutput voltage to a constant level.

In the experiments, the solar cell 201 and the solar cell 204 werearranged close to each other on a plane. Measurement of luminance isperformed using an illuminometer 510-02 manufactured by YokogawaElectric Corporation in such a manner that a distance from a lightsource and a surface of a solar cell is made equivalent to a distancefrom the light source and a light-receiving bulb of the illuminometer.Results of experiments indicated that boosting operation started at 800luxes. Adjustment of the oscillation frequency of the oscillator circuitvaried a boosting start voltage and the boosting start voltage was mostsensitive at an oscillation frequency of about 1 kHz to about 30 kHz. Ithas been demonstrated that when the output voltage of the solar cell 204used as a driving source of the booster circuit exceeds 0.95 V, theoscillator circuit 224 started oscillation but the switching element 208is not driven whereas when the illuminance was 1,100 luxes, the outputvoltage of the solar cell 204 was 1.4 V. Near a window or undersunlight, a sufficient boosting operation is obtained and the outputvoltage set by the divided resistors 240 and 243 was obtained from theoutput terminal 217.

FOURTH EXAMPLE

In a fourth example, a booster circuit of a boost converterconfiguration having an output control function is explained.

FIG. 8 is a diagram of a configuration of a booster circuit for anoutput of a solar cell that has a configuration of a boost converterwith an output control function and is not serially connected accordingto the fourth example of the present invention.

In the fourth example, similarly to the circuit configuration of thethird example shown in FIG. 7, the boosting capability of the boostercircuit 244 is controlled through the oscillation control terminal 260of the booster circuit 244 with the control output of the outputcontroller circuit to realize a constant voltage output operation. Adifference between this example and the third example is that when theoscillation control terminal 260 of the booster circuit 244 is at alogic low, the oscillator circuit operates to operate the boostercircuit, thus making unnecessary a bias circuit from the power sourceterminal 230 that is necessary in the third example. Since the operationof the oscillator circuit stops when the oscillation control terminal260 is at a logic high, a PNP transistor 272 or a P-type MOSFET levelshifter circuit is arranged downstream of the output of the comparator.Resistors 273 and 274 are bias resistors of the PNP transistor 272.

A resistor 270 is a pull-down resistor of the oscillation controlterminal 260 and a resistor 271 is to prevent excess current from thePNP transistor 272 and to prevent latch up by application of an excessvoltage to the oscillation control terminal. A capacitor 275 is toincrease the anti-noise characteristics of the oscillator circuitcontrol terminal.

Operation of the booster having this configuration is explained below.

When light is irradiated to solar cells and an output voltage isgenerated by the solar cell 204, the voltage of the power sourceterminal 230 increases and the Schmitt trigger type two-input NAND logicgate 74HC132 comes to be in an active state. Since there is no boostedoutput, the oscillation control terminal 260 is at a logic low due tothe pull-down resistor 270, so that the oscillator circuit startsoscillation and the booster circuit starts up to generate a boostedoutput. A voltage obtained by dividing the boosted output voltage by thedivided resistors 240 and 243 and the voltage of the standard voltagesource 242 are compared by the comparator 241. The comparator 241connects the positive and negative input terminals of the PNP transistor272 in a subsequent stage to each other in such a manner that when theboosted output voltage is higher than the voltage of the standardvoltage source 242, the PNP transistor 272 turns ON. When the transistorturns ON, current flows from the boosted output to the pull-downresistor 270, which brings the oscillation control terminal at a logichigh, resulting in that the oscillation operation stops and the boostingoperation stops.

When the output voltage is equal to or below the set voltage, the outputof the comparator turns OFF and the PNP transistor 272 turns OFF, sothat the oscillation control terminal 260 is at a logic low. As aresult, the oscillator circuit operates and the boosting operationstarts again, so that the output voltage is controlled to a constantvoltage.

The present invention should not be considered to be limited by theexamples, and various modifications and applications may be made withinthe scope of the appended claims.

With the booster of the present invention, even when the output voltageis 0.15 V or less, no problems occur and a boosted voltage can beobtained at a high efficiency. Therefore, there is no need forconnecting a number of single cells in series, so that the problemencountered in the conventional serially connected solar cells that whensome tens percents of single-cell solar cells that constitute a solarcell module is under a shade, the same effect as that obtained when sometens percents of the entire module is under a shade is obtained,resulting a considerable decrease in output, can be solved.

Conventionally, to prepare a serially connected solar cell module, acountermeasure of insulating wiring that connects a surface of a solarcell to a back surface of an adjacent solar cell and a portion betweencells is necessary. To increase the module packing ratio, a technique toreduce a space for wiring and a space for intercellular insulation ineach solar cell and to arrange cells with high precision, so that solarcells are at high cost. In contrast, by applying the present invention,serial connection becomes unnecessary, so that the cost of solar cellmodules decreases.

Conventionally, the shape of a cell is tetrangular and it has beendifficult to apply a design. However, according to the presentinvention, solar cells having various shapes can be used in a parallelconnection so that the solar cell modules are free of restrictions ontheir shape since the solar cells as a power generation target do nothave to be serially connected.

Fifth Embodiment

FIG. 9 is a block diagram of a configuration of a booster according to afifth embodiment of the present invention. The booster includes thebooster circuit 12 that boosts a low voltage output from a single-cellfuel cell 21 (i.e., the first cell) outputting a low voltage of about0.6 V to about 0.7 V (without loads) as a target to be boosted to apredetermined voltage (for example, a voltage at which the load canoperate) and a lithium storage cell 23 (i.e., the second cell) thatserves as a power supply unit for providing start-up energy to thebooster circuit 12. The fuel cell 21 merely supplies a low voltageoutput, a target to be boosted, to the booster circuit 12, and is not anessential constituent element of the booster of the present invention.

The fuel cell 21 is a single-cell fuel cell of a low voltage outputtingtype that can be produced without passing complicated productionprocesses such as configuring serial connection. The lithium storagecell 23 is a rechargeable secondary cell and plays a role of an energysource that provides start-up energy. The booster circuit 12 isconfigured by a circuit of, for example, a boost converter type, whichis easy to design a circuit configuration. By performing ON/OFF controlof the switching elements provided in the booster circuit, boosting of avoltage that is stored in a storage element such as a capacitor can beperformed. It is preferable to use a CMOS type circuit as an oscillatorcircuit for performing ON/OFF control of the switching elements.

Referring to FIG. 9, the operation of the booster of the presentinvention is explained. A chemical reaction is performed between a fueland oxygen (air) sent in the fuel cell 21 and the chemical reactiongenerates electric energy. The generated output is generally at a lowvoltage, for example, an output voltage of 0.6 V to 0.7 V without loads(i.e., when no load is connected) and at most about 0.3 V when a ratedoutput is generated. Therefore, the output from the fuel cell 21 cannotdirectly drive mobile devices such as note-type personal computers andmobile phones.

The low voltage output from the fuel cell 21 is input into the boostercircuit 12. In the booster circuit 12, boosted electric energy is storedin a storage element such as a capacitor (not shown). To operate thebooster circuit 12, a predetermined level of start-up energy isrequired. The lithium storage cell 23 supplies start-up energy to thebooster circuit 12. The booster circuit 12 requires some amounts ofenergy at the time of start-up but the booster circuit 12 can continuethe operation with a lower amount of energy than the energy given at thetime of start-up once the booster circuit 12 has started up.

For example, the boost converter type booster circuit requires an inputvoltage of about 1.4 V at the time of start-up. However, after thestart-up, the operation of the booster circuit 12 itself can becontinued even with a low input voltage of about 0.1 V. Therefore, inthe booster according to this embodiment, start-up energy is output fromthe lithium storage cell 23 to the booster circuit 12 only at the timeof the start-up. After the start-up, the output of the booster circuit12 itself is fed back to the booster circuit 12 as operation energy, sothat the operation of the booster circuit 12 itself can be continued toobtain a predetermined boosted output.

The output of the booster circuit 12, i.e., boosted output, can be setto any predetermined voltage depending on the operation voltage of themobile device to which the booster circuit 12 is connected, so that aboosted output for operating mobile devices can be obtained by utilizingthe energy of the fuel cell 21 from which only a low voltage output canbe obtained.

As explained above, with the booster according to this embodiment, a lowvoltage output, target to be boosted, from the first cell and start-upenergy from the second cell are input to the booster circuit whileoperation energy necessary for continuing the operation of the boostercircuit itself is fed back to the booster circuit by the booster circuititself, so that a predetermined boosted output can be obtained. As aresult, a boosted output for operating, for example, a mobile device canbe obtained by utilizing the energy of the first cell from which only alow voltage output is available and an increase in production costbecause of using a special cell can be prevented, so that a booster thatenables one to reduce cost by utilization of a versatile cell can beprovided.

In this embodiment, the fuel cell 21, which is the first cell, is asingle-cell fuel cell of a low voltage outputting type that can beproduced without passing complicated production processes such asconfigurating serial connection. However, a single-cell solar cell thatalso is of a low power outputting type and can be configured withoutserial connections may be used. Also, when it is desired to increase anoutput to the boosting circuit 12, parallelly connected fuel cells orsolar cells that can be realized without passing complicated productionprocesses may be used.

The lithium storage cell 23, which is the second cell, which is arechargeable secondary cell and plays a role of an energy source thatprovides start-up energy, may be any cell that can supply energy. Forexample, the lithium storage cell may be a primary cell that is notrechargeable, such as a dry cell. The second cell may be a storageelement such as an ordinary capacitor or an electric double layercapacitor.

Although it is preferable to use a CMOS type oscillator circuit as anoscillator circuit for performing ON/OFF control of the switchingelements in the booster circuit, other circuits, for example, a bipolartype oscillator circuit may be used. The bipolar type oscillator circuithas a disadvantage that the circuit consumes much power but has anadvantage that the minimum operation voltage is low. It is also possibleto design a circuit configuration making the best of this advantage.

Sixth Embodiment

FIG. 10 is a block diagram of a configuration of a booster according toa sixth embodiment of the present invention. The booster includes, inaddition to the configuration according to the fifth embodiment as shownin FIG. 9, a rectifier element 35 for outputting a part of the output ofthe booster circuit 12 to the lithium storage cell 23 as energy to beutilized for next and subsequent start-ups. Other configurations are thesame as or equivalent to those shown in FIG. 9 and the same referencenumerals designate those portions.

Referring to FIG. 10, the operation of this booster circuit isexplained. However, the feature that the booster circuit 12 performsboosting operation using the low voltage output from the single-cellfuel cell 21, the start-up energy from the lithium storage cell 23, andoperation energy that is a part of the own output and fed back to thebooster circuit is the same as that in the fifth embodiment andexplanation is omitted.

In the sixth embodiment, all or a part of the boosted output from thebooster circuit 12 is output to the lithium storage cell 23 through therectifier element 35. The energy output then is energy for starting theoperation of the booster circuit 12 again and is stored in the lithiumstorage cell 23. For example, when a low voltage output is not suppliedfrom the fuel cell 21 to the booster circuit 12, there is sometimes acase where it is desired that the operation of the booster circuit 12 bestopped to prevent unnecessary consumption of electric power. In thiscase, all or a part of the output of the booster circuit 12 is stored inthe lithium storage cell 23 and this energy is output to the boostercircuit 12 when the booster circuit 12 is restarted.

The rectifier element 35 is provided to prevent flow of current from thelithium storage cell 23 to the side of the output (booster circuit 12)when the stored voltage of the lithium storage cell 23 is higher thanthe boosted output.

With the booster according to this embodiment, a low voltage output,target to be boosted, from the first cell and start-up energy from thesecond cell are input to the booster circuit while operation energynecessary for continuing the operation of the booster circuit itself isfed back to the booster circuit by the booster circuit itself, so that apredetermined boosting output can be obtained. As a result, a boostingoutput for operating, for example, a mobile device can be obtained byutilizing the energy of the first cell from which only a low voltageoutput is available and an increase in production cost because of usinga special cell can be prevented, so that a booster that enables one toreduce costs by utilization of a versatile cell can be provided.

With the booster according to this embodiment, the booster circuitoutputs a boosted output to the second cell to store therein as start-upenergy for restarting the own operation of the booster circuit, so thatunnecessary consumption of electric power can be prevented. Sincerestart is possible with the energy stored in the second cell even whenthe boosted output decreases due to overload, thus falling in asituation where the own boosting operation of the booster circuit cannotbe continued, a configuration with which continued operation is easy canbe realized with ease.

While the lithium storage cell 23 may be a primary cell that is notrechargeable, such as a dry cell in the fifth embodiment, it isnecessary in the sixth embodiment to store energy for restarting thebooster circuit. Therefore, it is advantageous to use a storage elementsuch as an ordinary capacitor or an electric double layer capacitor inaddition to the rechargeable secondary cell.

Seventh Embodiment

FIG. 11 is a block diagram of a configuration of a booster according toa seventh embodiment of the present invention. The booster includes, inaddition to the configuration according to the sixth embodiment as shownin FIG. 10, a selector circuit 25 that has rectifier elements 36 and 37and selects which one of the start-up energy and operation energy is tobe output to the booster circuit 12. Other configurations are the sameas or equivalent to those shown in FIG. 9 and the same referencenumerals designate those portions.

Referring to FIG. 11, the operation of this booster circuit isexplained. A low voltage output is input to the booster circuit 12 fromthe fuel cell 21. Although in the fifth and sixth embodiments, both thestart-up energy and operation energy are input into the booster circuit,the booster circuit 12 according to the seventh embodiment is configuredin such a manner that either one of the start-up energy and operationenergy is input to the booster circuit 12 through the selector circuit25. The reason for this is as follows.

It is necessary to supply some input voltage to the booster circuit 12when starting up but once the booster circuit has started up, thebooster circuit 12 can continue its operation with a small amount ofinput voltage. That is, as in the configuration according to the seventhembodiment, inputting an output that is superior between outputs of thestart-up energy and operation energy to the booster circuit 12 throughthe selector circuit 25 can lead to realization of efficient utilizationof energy.

Unless both of a decrease in boosted output due to overload and adecrease in the energy stored in the lithium storage cell 23 occursimultaneously, restart of the booster circuit 12 is possible, so that asystem configuration with a high capacity utilization can be realizedwith ease.

The rectifier element 35 is provided so as to prevent flow of thecurrent from the lithium storage cell 23 to the output side when thestored voltage of the lithium storage cell 23 is higher than the boostedvoltage.

The rectifier elements 36 and 37 are provided in the selector circuit 25as units that supply a superior output (output having higher outputvoltage) between outputs of the start-up energy and operation energy tothe booster circuit 12.

With the booster according to the seventh embodiment, a low voltageoutput, target to be boosted, is input to the booster circuit 12 fromthe first cell and the selector circuit, to which both the start-upenergy and operation energy are input, outputs either one of thestart-up energy and operation energy to the booster circuit, so that notonly the boosted output for operating, for example, a mobile device canbe obtained by using the energy of the first cell from which only a lowvoltage output is available but also a booster with which an increase inproduction cost due to use of a special cell is prevented and reductionof cost by using a versatile cell is possible can be provided. Further,efficient utilization of boosted output energy can be realized and asystem configuration having a high capacity utilization can be realizedwith ease.

In the same manner as that in other embodiments, the first cell, whichis the fuel cell 21, may be a single-cell fuel cell or a single-cellsolar cell. Alternatively, parallelly connected fuel cells or solarcells may be used.

The second cell, which is the lithium storage cell 23, may be any cellthat can store energy for the restart similarly to the sixth embodiment.In addition to a rechargeable secondary cell, a storage element such asan ordinary capacitor or an electric double layer capacitor may be usedas the secondary cell.

Eighth Embodiment

FIG. 12 is a block diagram of a configuration of a booster according toan eighth embodiment of the present invention. The booster depictedincludes, in the configuration according to the fifth embodiment asshown in FIG. 9, a storage element 24 for storing the output of thebooster circuit 12 while the booster includes no lithium storage cell23. Other configurations are the same as or equivalent to those shown inFIG. 9 and the same reference numerals designate those portions.

Referring to FIG. 12, the operation of this booster circuit isexplained. In FIG. 12, a low voltage output is input to the boostercircuit 12 from the single-cell fuel cell 21. Here, although in thefifth and sixth embodiments, the start-up energy is input to the boostercircuit 12 from the lithium storage cell 23 and the operation energy isinput to the booster circuit 12 from the booster circuit 12 itself, thebooster circuit 12 according to the eighth embodiment is configured insuch a manner that both the start-up energy that is supplied whenstarting up and the operation energy that is continuously suppliedduring operation are input to the booster circuit 12 from the storageelement 24.

When the boosted output is directly supplied to a load with aconsiderable load fluctuation, load current changes greatly so that theboosted output fluctuates greatly. In such a case, a countermeasure thatis commonly adopted is to incorporate a constant voltage unit such asthe storage element 24 between the booster circuit 12 and the load (notshown) as shown in FIG. 12.

By providing the storage element 24 that provides a constant voltage,the start-up energy and operation energy output to the booster circuit12 caused to be output from the storage element 24 to thereby start upthe booster circuit 12 and continue its operation after the start-up.Accordingly, a configuration close to the actual system configurationcan be obtained and the booster circuit 12 can be made compact. Further,use of the storage element 24 enables one to realize a booster having arelatively large power source capacity. Further, use of the storageelement 24 enables one to realize a booster having a relatively largepower source capacity.

By the booster according to the eighth embodiment, a low voltage output,target to be boosted, is input to the booster circuit 12 from the firstcell and the selector circuit, to which both the start-up energy andoperation energy are input, outputs the start-up energy and operationenergy to the booster circuit. Accordingly, the boosted output foroperating, for example, a mobile device can be obtained by using theenergy of the first cell from which only a low voltage output isavailable. Also, a booster having a relatively large power sourcecapacity can be realized.

In the same manner as that in other embodiments, the first cell, whichis the fuel cell 21, may be a single-cell fuel cell or a single-cellsolar cell. Alternatively, parallelly connected fuel cells or solarcells may be used.

The storage element 24 may be a storage element such as an ordinarycapacitor or an electric double layer capacitor.

In the eighth embodiment, the booster circuit 12 and the storage element24 are configured to be separate. However, it is possible to configurethe booster in such a manner that the storage element 24 is incorporatedin the booster circuit 12.

Ninth Embodiment

FIG. 13 is a block diagram of a configuration of a booster according toa ninth embodiment of the present invention. The booster depicted isconfigured to include, in addition to the configuration according to theeighth embodiment as shown in FIG. 12, a selector circuit 26 that hasrectifier elements 45 and 46 and selects which one of the start-upenergy and operation energy is to be output to the booster circuit 12and a rectifier element 44 that prevents flow back from the storageelement 24 to the booster circuit 12. Other configurations are the sameas or equivalent to those shown in FIG. 12 and the same referencenumerals designate those portions.

Referring to FIG. 13, the operation of this booster circuit isexplained. A low voltage output is input to the booster circuit 12 fromthe single-cell fuel cell 21. Although in the eighth embodiment, boththe start-up energy that is supplied when starting up and the operationenergy that is continuously supplied during the operation are input tothe booster circuit from the storage element 24, the booster circuit 12according to this embodiment is configured in such a manner that onlythe operation energy is supplied by the booster circuit 12.

In the selector circuit 26 shown in FIG. 13, a superior output betweenoutputs of the start-up energy and the operation energy is supplied tothe booster circuit 12 through the selector circuit 26. That is, whenthe booster is started up, usually the booster circuit 12 is in a statewhere the operation stops and hence the output voltage of the storageelement 24 (start-up energy) is higher than the output voltage of thebooster circuit 12 (operation energy). Accordingly, the start-up energyis supplied to the booster circuit 12 through the rectifier element 46.

On the other hand, during the operation, the output voltage of thebooster circuit 12 (operation energy) is higher than the output voltageof the storage element 24 (start-up energy). Accordingly, the operationenergy is supplied to the booster circuit 12 itself through therectifier element 45.

In this configuration, for example, when a load having a large loadfluctuation is connected to the storage element 24, the load on thestorage element 24 increases. Even in such a case, the configuration inwhich the operation energy for allowing the booster circuit 12 tocontinue its operation is supplied by the booster circuit 12 itselfenables a reduction of the load on the storage element 24.

With the booster according to this embodiment, a low voltage output,target to be boosted, is input to the booster circuit 12 from the firstcell and the selector circuit, to which both the start-up energy that isan output from the storage element and the operation energy that is anoutput from the booster circuit are input, outputs either one of thestart-up energy and operation energy to the booster circuit.Accordingly, the boosted output for operating, for example, a mobiledevice can be obtained by using the energy of the first cell from whichonly a low voltage output is available. Also, a booster with which anincrease in production cost due to use of a special cell is preventedand a reduction of cost by using a versatile cell is possible can beprovided. The load on the storage element can be reduced and efficientutilization of boosted output energy can be realized.

In the same manner as that in other embodiments, the first cell, whichis the fuel cell 21, may be a single-cell fuel cell or a single-cellsolar cell. Alternatively, parallelly connected fuel cells or solarcells may be used.

The storage element 24 may be a storage element such as an ordinarycapacitor or an electric double layer capacitor.

In the eighth embodiment, the booster circuit 12 and the storage element24 are configured to be separate. However, it is possible to adopt aconfiguration in which the storage element 24 and the rectifier element44 are incorporated in the booster circuit 12.

Tenth Embodiment

FIG. 14 is a block diagram of a configuration of a booster according toa tenth embodiment of the present invention. The booster depictedincludes, in the configuration according to the fifth embodiment asshown in FIG. 9, a detecting unit 29 that detects whether a fuel oroxygen (air) is supplied to the fuel cell 21, a switching unit 27provided with a switching element 51 that is connected between thelithium storage cell 23 and the booster circuit 12 and to which astart-up signal from the detecting unit 29 and a supply stop signal fromthe booster circuit 12 are input. Other configurations are the same asor equivalent to those shown in FIG. 9 and the same reference numeralsdesignate those portions.

Referring to FIG. 14, the operation of this booster circuit isexplained. In FIG. 14, the detecting unit 29 detects that a fuel oroxygen (air) (hereinafter, referred to as “fuel etc.”) is supplied tothe fuel cell 21 and outputs a start-up signal. The booster circuit 12generates a boosted output formed by boosting a low voltage output fromthe fuel cell 21. The switching unit 27 controls whether to output thestart-up energy supplied from the lithium storage cell 23 to the boostercircuit 12 based on the start-up signal that is output from thedetecting unit 29 and the supply stop signal that is output from thebooster circuit 12. On the other hand, the output of the booster circuit12 is fed back to the booster circuit 12 itself, so that the boostercircuit 12 can continue its boosting operation.

The detecting unit 29 outputs a start-up signal while the fuel etc. issupplied to the fuel cell 21. The start-up signal is output while thefuel etc. is supplied (start-up signal “ON”), and acts in such a mannerthat the switching element 51 of the switching unit is conducting. Onthe other hand, the supply stop signal is the boosted output itself ofthe booster circuit 12 and acts in such a manner that when the boostedoutput voltage is a predetermined voltage or more (supply stop signal“ON”), the switching element 51 of the switching unit 27 is interruptedwhile when the boosted output voltage is less than the predeterminedvoltage (supply stop signal “OFF”), the switching element 51 isconducting.

The relationship between the start-up signal and supply stop signal andthe switching unit 27 is as follows. That is, when the start-up signalis in a state of ON and the supply stop signal is in a state of OFF, theswitching element 51 is conducting and the start-up energy is suppliedfrom the lithium storage cell 23 to the booster circuit 12.

When the start-up signal is in a state of OFF, or the supply stop signalis in a state of ON, the switching element 51 is interrupted, so thatthere is no supply of the start-up energy to the booster circuit 12.

The booster according to this embodiment is in as state where the fueletc. is supplied to the fuel cell, and when the booster circuit 12 hasnot started up yet, the start-up energy is output to the booster circuit12 from the lithium storage cell 23. In short, efficient use of thestart-up energy is made possible by controlling in such a manner thatthe start-up energy is output only when it is necessary to start up thebooster circuit 12.

FIG. 15 is a block diagram of the switching unit 27 shown in FIG. 14with serially connected switching elements 51 a and 51 b. The functionof the switching unit 27 shown in FIG. 14 can be easily realized byconnecting the start-up signal to the switching element 51 a and thesupply stop signal to the switching element 51 b.

With the booster according to the tenth embodiment, the switching unitto which a low voltage output from the first cell is input controlswhether to allow the start-up energy supplied from the second cell to beoutput to the booster circuit based on the start-up signal output fromthe detecting unit and the supply stop signal that is the boosted outputitself, so that the boosted output for operating, for example, a mobiledevice can be obtained by using the energy of the first cell from whichonly a low voltage output is available. Also, the start-up energy can beoutput only when it is necessary to start up the booster circuit, sothat it is possible to use the start-up energy efficiently.

The feature of this embodiment, i.e., the configuration in whichcontrols whether to allow the start-up energy supplied from the secondcell to be output to the booster circuit are performed based on thestart-up signal output from the detecting unit and the supply stopsignal that is the boosted output itself can be applied to the eighthand ninth embodiments with similar effects as those of the tenthembodiment.

The lithium storage cell 23, which is the second cell, which is arechargeable secondary cell and plays a role of an energy source thatprovides start-up energy, may be any cell that can supply energy. Forexample, the lithium storage cell may be a primary cell that is notrechargeable, such as a dry cell. In addition, the second cell may be astorage element such as an ordinary capacitor or an electric doublelayer capacitor.

Eleventh Embodiment

FIG. 16 is a block diagram of a configuration of a booster according toan eleventh embodiment of the present invention. The booster includes,in addition to the configuration according to the tenth embodiment asshown in FIG. 14, the selector circuit 25 that has the rectifierelements 36 and 37 and selects which one of the start-up energy andoperation energy is to be output to the booster circuit 12 and therectifier element 35 for outputting all or a part of the output of thebooster circuit 12 to the lithium storage cell 23. Other configurationsare the same as or equivalent to those shown in FIG. 14 and the samereference numerals designate those portions.

Referring to FIG. 16, the operation of this booster circuit isexplained. However, the operation of the detecting unit to output astart-up signal and the operation of the fuel cell 21 to supply a lowvoltage output to the booster 12 are the same as those in the tenthembodiment and description thereof is omitted.

In the eleventh embodiment, all or a part of the boosted output from thebooster circuit 12 is output to the lithium storage cell 23 through therectifier element 35. Similarly to the sixth embodiment, the rectifierelement 35 is provided so as to prevent a backflow of current from thelithium storage cell 23 to the booster circuit 12.

The switching unit 27 controls whether to output the start-up energysupplied from the lithium storage cell 23 to the booster circuit 12based on the start-up signal output from the detecting unit 29. Thestart-up signal is output is a start-up signal (“ON” signal) forconducting the switching unit 27 while the fuel etc. is being supplied.On this occasion, the energy from the lithium storage cell 23 is outputto the selector circuit 25.

The selector circuit 25 outputs to the booster circuit 12 a superioroutput between outputs of the start-up energy that is output from theswitching unit 27 and the operation energy that is a boosted output fromthe booster circuit 12. The booster circuit 12 to which the start-upenergy or operation energy is supplied generates and outputs apredetermined boosted output.

With the booster according to the eleventh embodiment, a low voltageoutput, target to be boosted, is input to the booster circuit from thefirst cell and the selector circuit, to which both the start-up energyand operation energy are input through the switching unit that operatesbased on the start-up signal output from the detecting unit, outputseither one of the start-up energy and operation energy to the boostercircuit. Accordingly, not only the boosted output for operating, forexample, a mobile device can be obtained by using the energy of thefirst cell from which only a low voltage output is available but also abooster with which an increase in production cost due to use of aspecial cell is prevented and a reduction of cost by using a versatilecell is possible can be provided. Also, the start-up energy can beoutput only when it is necessary to start up the booster circuit, sothat it is possible to use the start-up energy efficiently.

The feature of this embodiment, i.e., the configuration in which thestart-up energy is output based on the start-up signal output from thedetecting unit and a control whether to allow either the start-up energyor the operation energy to be output to the booster circuit is performedcan be applied to the eighth and ninth embodiments with similar effectsas those of the eleventh embodiment.

The lithium storage cell 23, which is the second cell, which is arechargeable secondary cell and plays a role of an energy source thatprovides start-up energy, may be any cell that can supply energy. Forexample, the lithium storage cell may be a primary cell that is notrechargeable, such as a dry cell. In addition, the second cell may be astorage element such as an ordinary capacitor or an electric doublelayer capacitor.

Twelfth Embodiment

FIG. 17 is a block diagram of a configuration of a booster according toa twelfth embodiment of the present invention. The booster is configuredin such a manner that in the configuration according to the eleventhembodiment as shown in FIG. 16, the start-up signal to be output to theswitching unit 27 is output as follows. That is, a power generationrequest signal to be given to control valves 42 and 43 for controllingfuel and oxygen (air), respectively, supplied to the fuel cell 21 isoutput through a signal delay circuit 28 as the start-up signal. Otherconfigurations are the same as or equivalent to those shown in FIG. 16and the same reference numerals designate those portions.

Referring to FIG. 17, the operation of this booster circuit isexplained. When a power generation request signal is input to thecontrol valves 42 and 43, the control valves 42 and 43 are opened andfuel and oxygen are supplied to the fuel cell 21. The power generationrequest signal is input to the signal delay circuit 28. The signal delaycircuit 28 outputs to the switching unit 27 a signal that is delayed apredetermined time with respect to the input power generation requestsignal.

A certain time is required for fuel and oxygen to distribute in the fuelcell. Therefore, by delaying a timing in which the switching unit 27turns ON by a predetermined time behind a timing in which fuel andoxygen are sent to the fuel cell 21, the timing in which the output ofthe fuel cell 21 is output to the booster circuit 12 and the timing inwhich the start-up energy is output to the booster circuit 12 aresynchronized with each other so that efficient use of the start-upenergy is possible.

A delay time that is delayed by the signal delay circuit 28 only needsto be set to a time from a time when the power generation request signalis input to when the fuel etc. is distributed in the inside of the fuelcell 21 and may be set to any time depending on the system of the fuelcell. Note that the operation thereafter is similar to that in theeleventh embodiment, and a predetermined boosted output can be obtainedby the booster circuit 12 can provide.

With the booster according to this embodiment, a low voltage output,target to be boosted, is input to the booster circuit from the firstcell and the selector circuit, to which both the start-up energy throughthe switching unit that operates based on the start-up signal output andthe operation energy as an output of the booster circuit are input,outputs either one of the start-up energy and operation energy to thebooster circuit. Accordingly, not only the boosted output for operating,for example, a mobile device can be obtained by using the energy of thefirst cell from which only a low voltage output is available but also abooster with which an increase in production cost due to use of aspecial cell is prevented and a reduction of cost by using a versatilecell is possible can be provided. Also, the start-up energy can beoutput only when it is necessary to start up the booster circuit, sothat it is possible to use the start-up energy efficiently.

The feature of this embodiment, i.e., the configuration in which thestart-up energy is output based on the delayed output of the powergeneration request signal and a control whether to allow either thestart-up energy or the operation energy to be output to the boostercircuit is performed can be applied to the eighth and ninth embodimentswith similar effects as those of the twelfth embodiment.

The lithium storage cell 23, which is the second cell, which is arechargeable secondary cell and plays a role of an energy source thatprovides start-up energy, may be any cell that can supply energy. Forexample, the lithium storage cell may be a primary cell that is notrechargeable, such as a dry cell. In addition, the second cell may be astorage element such as an ordinary capacitor or an electric doublelayer capacitor.

Thirteenth Embodiment

FIG. 18 is a block diagram of a configuration of a booster according toa thirteenth embodiment of the present invention. The booster includesthe booster circuit 12 that boosts a low voltage output from a powergenerating element 20 as a target to be boosted to about a predeterminedvoltage (for example, a voltage at which a load to be connected canoperate) and an auxiliary booster circuit 13 provided to give start-upenergy to the booster circuit 12. The power generating element 20, whichsupplies a low voltage output, a target to be boosted, to the boostercircuit 12, is not a constituent element of the booster of the presentinvention.

The power generating element 20 that can be used include, for example, asingle-cell fuel cell that outputs a low voltage as low as about 0.6 Vto about 0.7 V without loads, and single-cell soar cells that have acomposition of a monocrystalline silicon, polycrystalline silicon,amorphous silicon, and a compound semiconductor and output a low voltageof at most a little higher than 0.5 V.

The booster circuit 12 includes, for example, a switching regulator typecircuit, with which it is easy to design a circuit configuration, and aboosted output can be obtained by generating energy ofcounterelectromotive force by ON/OFF control of the switching elementprovided in the booster circuit itself and storing the energy in astorage element such as a capacitor in the inside of the booster circuititself.

The auxiliary booster circuit 13 includes, for example, a switchedcapacitor type circuit or a charge pump type circuit. The feature of theauxiliary booster circuit 13 is that the auxiliary booster circuit 13can start-up at a low voltage as low as about 0.2 V to about 0.3 V andprovides an output voltage of 1.2 V to 3 V depending on the number ofconnection stages of the storage elements. Therefore, the boostercircuit 12 can be started up based on the start-up energy supplied bythe auxiliary booster circuit 13. The details of the switched capacitortype circuit and of the charge pump type circuit are explained.

Referring to FIG. 18, the operation of the booster is explained.Electric energy is generated in the power generating element 20. Anoutput based on the generated electric energy is generally at a lowvoltage. For example, in fuel cells, the output is about 0.6 to about0.7 V in the absence of loads or at most around 0.3 V when rated outputis produced. In solar cells, the output is at most a little higher than0.5 V when it is fine or at most around 0.3 V when it is clouded. Thatis, the output from the power generating element 20 alone cannotdirectly allow a mobile device such as a note type personal computer ora mobile phone to operate.

The low voltage output from the power generating element 20 is input tothe booster circuit 12. In the booster circuit 12, boosted electricenergy is accumulated in a storage element such as a capacitor (notshown). On the other hand, a predetermined amount of start-up energy isrequired for operating the booster circuit 12. The auxiliary boostercircuit 13 supplies a start-up voltage to the booster circuit 12. Thebooster circuit 12 requires about 1 V when starting up but it isfeatured that a small amount of start-up current is sufficient.Therefore, in the booster according to the thirteenth embodiment, thebooster circuit 12 is started up with the start-up voltage from theauxiliary booster circuit 13 when starting up, and after the start-up,the own output is fed back to the booster circuit 12 as operation energyfor continuing the operation of the booster circuit 12 to obtain aboosted output. This configuration has an advantage that no power supplyunit is necessary for starting up the booster circuit.

Referring to a specific example of the booster circuit, for example, inthe case of a general switching regulator type booster circuit, an inputvoltage of about 0.9 V to about 1.2 V is necessary when starting upwhile after the start-up, the operation of the booster circuit 12 itselfcan be continued even with a low input voltage of about 0.1 V.

The output of the booster circuit 12, that is, a boosted output, can beset at any predetermined voltage depending on the operation voltage of,for example a mobile device to be connected. Therefore, a predeterminedboosted output for operating a mobile device or the like can be obtainedby utilizing the energy of the power generating element 20 that canprovide only a low voltage output.

A principle of operation and so on of a switched capacitor type circuitor a charged pump type circuit as a specific example of the auxiliarybooster circuit 13 is explained.

FIG. 19 is a schematic for explaining a principle of operation of aswitched capacitor type. V_(dd) designates a direct current voltage andcorresponds to the low voltage output that is output by the powergenerating element 20 shown in FIG. 18. SW₁₁ to SW₁₅ and SW₂₁ to SW₂₈designate switching elements of a MOSFET or the like and controlled toeither one of a state of ON and a state of OFF by, for example, acontroller circuit not shown. Capacitors C₁₁ to C₁₅ are storage elementsfor storing charge. In particular, the capacitor C₁₅ is a storageelement that stores start-up energy (output of the auxiliary boostercircuit) for starting up the booster circuit 12.

Referring to FIG. 19, the operation of the switched capacitor typecircuit is explained. First, in the state as shown in the upper part ofFIG. 19, all of SW₂₁ to SW₂₈ are in a state of ON (closed) and all ofSW₁₁ to SW₁₅ are in a state of OFF (open). Then, the capacitors C₁₁ toC₁₅ are in as state where they are connected in parallel on the part ofthe direct current voltage V_(dd), so that the capacitors C₁₁ to C₁₅ arecharged (charge is accumulated) to a voltage of approximately V_(dd).

When all of SW₂₁ to SW₂₈ are set to be in a state of OFF and all of SW₁₁to SW₁₅ are set to be in a state of ON as shown in the lower part ofFIG. 19 from this state, the capacitors SW₁₁ to SW₁₅ are connected inseries on the part of the direct current V_(dd). Then, the potential ofthe upper end of the capacitor C₁₄ is 5V_(dd), so that a voltage (outputof the auxiliary booster circuit) of 5V_(dd) can be generated across thecapacitor C₁₅. An increasing number of connected stages results in afurther increase in an output voltage. On the other hand, with onestroke of switching operation, a current capacity for operating thebooster circuit 12 cannot be secured. Accordingly, a predeterminedcurrent capacity can be secured by repeatedly performing the switchingoperation.

FIG. 20 is a schematic for explaining a circuit configuration and aprinciple of operation of a charge pump type. V_(dd) designates a directcurrent voltage and corresponds to the low voltage output that is outputby the power generating element 20 shown in FIG. 18. Reference symbolsSW₃₁ to SW₃₅ and SW₄₁ to SW₄₈ designate switching elements of a MOSFETor the like and controlled to either one of a state of ON and a state ofOFF by, for example, a controller circuit not shown. Capacitors C₃₁ toC₃₅ are storage elements for storing charge. In particular, thecapacitor C₃₅ is a storage element that stores start-up energy (outputof the auxiliary booster circuit) for starting up the booster circuit12. The charged pump type circuits, like the switched capacitor typecircuits, can be constituted by capacitors and switching elements alone.

Referring to FIG. 20, the operation of the charged pump type circuit isexplained. In the state shown in the upper part of FIG. 20, SW₃₁, SW₃₃,and SW₃₅ are in a state of ON and SW₃₂ and SW₃₄ are in a state of OFF.On the other hand, SW₄₁, SW₄₄, SW₄₅, and SW₄₈ are in a state of ON whileSW₄₂, SW₄₃, SW₄₆, and SW₄₇ are in a state of OFF. The capacitor C₃₁ ischarged (charge is accumulated) to approximately a voltage of V_(dd) anda potential V1 on the upper end of the capacitor C₃₁ becomesapproximately V_(dd). As will be apparent in the subsequent operation,the capacitors C₃₂, C₃₃, and C₃₄ are charged to voltages ofapproximately 2V_(dd), 3V_(dd), and 4V_(dd), respectively, so thatpotentials V₂, V₃, V₄, and V₅ of the respective upper ends of thecapacitors C₃₂, C₃₃, C₃₄ and C₃₅ become approximately 3V_(dd), 4V_(dd),5V_(dd), and 5V_(dd), as shown in FIG. 20.

When all the states of the switching elements are reversed from thisstate, the states as shown in the middle part of FIG. 20 appears. Onthis occasion, since SW₄₂ is in a state of ON, and SW₃₂ and SW₄₃ are ina state of ON, the capacitor C₃₁ is charged up to approximately 2V_(dd),so that the potential V2 on the upper end of the capacitor C₃₂ becomesapproximately 2V_(dd). That is, transition of the state in the upperpart of FIG. 20 to the state in the middle part of FIG. 20 results intransfer of the charge from the first stage (capacitor C₃₁) to thesecond stage (capacitor C₃₂). This relationship is the same also betweenthe third stage (capacitor C₃₃) and the fourth stage (capacitor C₃₄).

When all the states of the switching elements are reversed from thisstate (that is, into the same switching states as those in the upperpart), the states as shown in the lower part of FIG. 20 appears. In thiscondition, the charge is transferred from the power generation element(V_(dd)) to the first stage, between the second stage (capacitor C₃₂)and the third stage (capacitor C₃₃), and between the fourth stage(capacitor C₃₄) and the fifth stage (capacitor C₃₅). The charged pumptype circuit shown in FIG. 20 is configured to secure a predeterminedvoltage and a predetermined current capacity in the same manner as thatof the switched capacitor type circuit by repeating such a bucket-relaytype charge transfer alternately.

The switched capacitor type circuit and charged pump type circuit usedas the auxiliary booster circuit 13 have low boosting capability and lowboosting efficiency as compared with the switching regulator typecircuit and the like used as the booster circuit 12. If switchingregulator type circuits are named high efficiency large power typebooster circuits, switched capacitor type circuits and charged pump typecircuits can be named low efficiency small power type booster circuits.

However, switched capacitor type circuits and charged pump type circuitscan be configured by capacitors and switching elements such as MOSFETsalone. The switching elements such as MOSFETs can perform switchingoperation at a low voltage of about 0.2 V to 0.3 V. On the other hand,switching regulator type circuit requires a start-up voltage of 0.9 V ormore but requires not so much of a start-up current. Therefore, use of aswitched capacitor type circuit or a charged pump type circuit forstarting up a switching regulator type circuit enables one to utilizeboth the features effectively.

That is, it is possible to arrange the booster circuit of a lowefficiency small power type between a power generating element of whichthe power generation voltage is not made so high and the booster circuitof a high efficiency large power type so as to operate in such a mannerthat the defects of both can be compensated.

With the booster according to the thirteenth embodiment, an output ofthe auxiliary booster circuit, which is start-up energy necessary forthe start-up of the booster circuit 12 itself, is input to the boostercircuit 12, or operation energy necessary for continuing the operationof the booster circuit 12 itself is fed back from the booster circuit 12itself. This leads to generation of a boosted output based on the lowvoltage output supplied as a target to be boosted. Accordingly, thebooster circuit can be started up independently of the start-up energyfrom a power supplying unit other than the power generating element.

Fourteenth Embodiment

FIG. 21 is a diagram of a configuration of a booster according to afourteenth embodiment of the present invention. The booster isconfigured to efficiently utilize the generated energy of the powergenerating element. The configuration shown in FIG. 21 is designed insuch a manner that in the configuration according to the thirteenthembodiment as shown in FIG. 18, a control signal for judging whether tostop the start-up of the auxiliary booster circuit 13 is output from thebooster circuit 12 to the auxiliary booster circuit 12.

Referring to FIG. 21, the operation of the booster is explained.However, the feature that the booster circuit 12 performs boostingoperation by using either one of the start-up energy from the auxiliarybooster circuit 13 and the operation energy obtained by feeding back apart of the output of the booster circuit 12 itself is the same as thefirst embodiment, so that description thereof is omitted.

The booster according to the fourteenth embodiment is configured in sucha manner that after the start-up of the booster circuit 12, a controlsignal is output from the booster circuit 12 to the auxiliary boostercircuit 13 to stop the supply of the operation energy that is output tothe booster circuit 12 from the auxiliary booster circuit 13. A boostedoutput itself that is output from the booster circuit 12 can be used asthe control signal. The judgment whether to stop the supply of thestart-up energy may be performed based on the level of the boostedoutput. For example, control can be performed in such a manner that whenthe level of the boosted output exceeds a predetermined value, thesupply of the operation energy stops while when the level of the boostedoutput is less than the predetermined value, the supply of the operationenergy continues. Control of operation/non-operation in the inside ofthe auxiliary booster circuit 13 can be performed by stopping anoscillator circuit that switches the switched capacitor circuit uponreceipt of a control signal therefor.

As described above, by the booster according to the fourteenthembodiment, the start-up of the auxiliary booster circuit is controlledbased on the boosted output, so that after the start-up of the boostercircuit, all of the generated energy of the power generating element canbe directed to power generation, thereby promoting efficient utilizationof generated energy.

Fifteenth Embodiment

FIG. 22 is a diagram of a configuration of a booster according to afifteenth embodiment of the present invention. The booster is of aconfiguration which includes an output control circuit 16 a that isconnected to an output stage of the booster circuit 12 in series. Otherconfigurations are the same as or equivalent to those in the fourteenthembodiment and the same reference numerals as those in each circuitshown in FIG. 21 designate those portions.

Referring to FIG. 22, the operation of this booster circuit isexplained. However, the feature that the booster circuit 12 performsboosting operation using either one of the start-up energy from theauxiliary booster circuit 13 and the operation energy obtained byfeeding back a part of the output of the booster circuit 12 itself isthe same as those in the first and second embodiments, so thatdescription thereof is omitted.

The boosted output that is boosted by the booster circuit 12 is output,for example, as a constant voltage output by an output controllercircuit 16 a and a stable constant voltage output is supplied to a load(not shown). Further, in the same manner as in that in the fourteenthembodiment, when a predetermined boosted output is provided, the outputof the start-up energy from the auxiliary booster circuit 13 stops basedon the control signal (start-up stop control signal) from the boostercircuit 12.

When the power generating element 20 is an energy source such as a solarcell, the output of the output controller circuit 16 a is made aconstant current output and a secondary cell for storing this energy maybe directly connected to the output control circuit 16 a. In addition, arectifier element may be connected between the output controller circuit16 a and the secondary cell. Also, the secondary cell may be connectedbetween the output controller circuit 16 a and the power generatingelement 20 may be connected between the output controller circuit 16 aand the secondary cell through a rectifier element. With suchconfigurations, the flow back of current from the secondary cell to theoutput controller circuit 16 a can be prevented, so that unnecessarydischarge of the secondary cell can be prevented.

FIG. 23 is a diagram of a configuration that includes a constant voltageelement (Zener diode) as one example of the output controller circuit 16a. FIG. 24 is a diagram of a configuration that includes a constantvoltage element 61 (Zener diode) and a constant current element 62 asone example of the output controller circuit 16 a. As shown in FIGS. 22and 23, a constant voltage output or a constant current output can beeasily generated so that a booster having an output control function canbe realized at low cost and in a compact form. As another configurationof the output controller circuit 16 a, a 3-terminal series regulator orthe like may be used. This increases the stability of the outputvoltage.

With the booster according to the fifteenth embodiment, the outputcontrol is performed for obtaining a constant voltage or constantcurrent, so that in addition to the effects of the first and secondembodiments, respectively, the effect of supplying a stable output to aload can be obtained.

Sixteenth Embodiment

FIG. 25 is a diagram of a configuration of a booster according to asixteenth embodiment of the present invention. The booster is of aconfiguration which includes an output control circuit 16 b that isconnected to an output stage of the booster circuit 12 in parallel.Other configurations are the same as or equivalent to those in thefourteenth embodiment and the same reference numerals as those in eachcircuit shown in FIG. 21 designate those portions.

Referring to FIG. 25, the operation of this booster circuit isexplained. However, the feature that the booster circuit 12 performsboosting operation using either one of the start-up energy from theauxiliary booster circuit 13 and the operation energy obtained byfeeding back a part of the output of the booster circuit 12 itself andthe feature that when a predetermined boosted output is obtained, theoutput of the start-up energy from the auxiliary booster circuit 13stops based on the control signal from the booster circuit 12 are thesame as the fourteenth embodiment, so that description thereof isomitted.

The boosted output that is boosted by the booster circuit 12 issubjected to feedback control by the output controller circuit 16 b andis output as a constant voltage variable output. That is, the boosteraccording to the sixteenth embodiment has a function to maintain theoutput of the booster circuit 12 at a constant voltage by the outputcontrol circuit 16 b and vary the output voltage in accordance with aload capacity. This constant voltage varying function can be realized bya configuration in which the booster circuit 12 includes a circuit of aswitching type and the output control circuit 16 b performs control suchas pulse width modulation (PWM) control or pulse frequency modulation(PFM) control to the booster circuit 12.

FIG. 26 is a diagram of one example of a configuration of the outputcontroller circuit 16 b. The output control circuit 16 b includes a timeratio modulator circuit 64, an oscillator circuit 65, and a comparatorcircuit 66. The output control circuit 16 b operates as follows. Thecomparator 66 in the output controller circuit 16 b compares the outputof the booster circuit 12 and a predetermined standard voltage value 67and a differential output voltage between these outputs is output to thetime ratio modulator circuit. Time ratio modulator circuit 64 generates,for example, a PWM control signal to a triangular wave that is outputfrom the oscillator circuit 65 based on the differential output voltagethat is output from the comparator circuit 66 and outputs it to thebooster circuit 12. In the circuit configuration according to thisembodiment, as described above, a configured is adopted in such a mannerthat the boosted output of the booster circuit 12 is subjected tofeedback control by the output controller circuit 16 b, so that theoutput voltage is stabilized. A configuration is adopted in such amanner that the output voltage can vary based on the standard voltagevalue 67, so that a variable output of a constant voltage can beobtained.

With the booster according to the sixteenth embodiment, a boosted outputof the booster circuit 12 is subjected to feedback control by the outputcontroller circuit 16 b and the output voltage is made variable based onthe standard voltage, so that in addition to the effects of the first tothird embodiments, a variable and stabilized output can be obtained inaccordance with a load capacity.

Seventeenth Embodiment

FIG. 27 is a diagram of a configuration of a booster according to aseventeenth embodiment of the present invention. The booster depicted inFIG. 27 is configured in such a maimer that in the booster according tothe fifteenth embodiment shown in FIG. 22, a control signal istransmitted from the output control circuit 16 a to the booster circuit12 to make the boosting capability variable, thereby achieving a controlobjective. Other configurations are the same as or equivalent to thoseof the fifteenth embodiment and the same reference numerals as thoseshown in FIG. 22 designate those portions.

Referring to FIG. 27, the operation of this booster circuit isexplained. The booster circuit 12 receives start-up energy from theauxiliary booster circuit 13 and starts up. In this point in time, noboosted output is generated or a boosted output does not reach theminimum operation voltage of the output controller circuit 16 a.Therefore, in this point in time, no control signal from the outputcontroller circuit 16 a is present or an unstable control signal ispresent. For this reason, there is a fear that the booster circuit 12that has come to start up will stop due to an undesirable state of thecontrol signal, thus failing to operate normally. To solve this problem,a circuit configuration having the following characteristics must beadopted.

(1) At the time of start-up, an unstable control output is not given tothe booster circuit 12 from the output controller circuit 16 a.

(2) At the time of start-up, the control signal output terminal of theoutput controller circuit 16 a is at a high impedance.

To prevent the output controller circuit 16 a from outputting anunstable control signal, it is effective to use a current drivingelement such as a bipolar transistor in a control signal outputtingstage. When such an element is used, a predetermined current isnecessary for turning the element ON, so that wrong operation of theelement can be prevented at the time of starting up the booster circuit12 or after the start-up thereof. Making the output terminal at a highimpedance results in a flow of current from the booster circuit 12 tothe control output terminal of the output control circuit 16 a, so thatdeterioration of the start-up characteristics of the booster circuit canbe prevented. Therefore, it is effective to adopt open drainconfiguration that is made a current-driven type by connecting aresistor in parallel to the open collector or to between the gate andsource in a control signal output stage of the output controller circuit16 a.

In the booster according to the seventeenth embodiment, the boostercircuit controls boosting capability based on the control output of theoutput controller circuit. Accordingly, the output controller circuit isprevented from performing an undesirable control to the booster circuitthat has just come to start up and is in an unstable state, such as astate immediately after the start-up.

Eighteenth Embodiment

FIG. 28 is a diagram of a configuration of a booster according to aneighteenth embodiment of the present invention. The booster includes, inthe configuration according to the thirteenth embodiment shown in FIG.18, a storage element 58 that stores a part of the output of the boostercircuit 12 as energy to be used upon a next or subsequent start-up, arectifier element 68 for preventing flow back that prevents flow of theoutput of the storage element 58 to the load side, and a selectorcircuit 70 including rectifier elements 72 and 73 for selecting eitherone of the auxiliary booster circuit 13 and the storage element 58 as asource that provides start-up energy. Other configurations are the sameas or equivalent to those of the fifteenth embodiment and the samereference numerals as those shown in FIG. 18 designate those portions.

Referring to FIG. 28, the operation of this booster circuit isexplained. However, the feature that the booster circuit 12 performsboosting operation using the operation energy that is a part of its ownoutput fed back to the booster circuit itself after the start-up is thesame as that in the other embodiments and explanation will be omittedherein.

In FIG. 28, the booster circuit 12 receives either one of the start-upenergy form the auxiliary booster circuit 13 and the start-up energyfrom the storage element 58 and starts up. In the selector circuit 70provided with the rectifiers 72 and 73, one of the output voltage of theauxiliary booster circuit 13 and the output voltage of the storageelement 58, which is higher, is selected and output to the boostercircuit 12. After the start-up, the booster circuit 12 supplies apredetermined boosted output to, for example, a load (not shown). A partof the boosted output is stored in the storage element 58 through therectifier element 68 as energy for restarting the booster circuit 12.

In the boosters according to other embodiments, when a predeterminedoutput (power generation energy) is not provided to the booster circuit12 from the power generating element 20, the operation of the boostercircuit 12 becomes unstable, so that it becomes necessary to stop thebooster circuit 12. On the other hand, to restart the booster circuit 12after the booster circuit 12 stops, new start energy is required. Inthis case, if all or a part of the output of the booster circuit 12 isstored in the storage element 58 as energy for restarting the boostercircuit 12 itself, not only the start-up energy from the auxiliarybooster circuit 13 but also the start-up energy from the storage element58 can be used when the booster circuit 12 is restarted. If the boostercircuit can be restarted using the start-up energy from the storageelement 58, not only the restart time of the booster circuit 12 can beshortened as compared with the case where the auxiliary booster circuit13 is used but also the booster circuit 12 can be started up reliably.If the predetermined boosted output is output from the booster circuit12, similarly to the fourteenth embodiment, it is only necessary to stopoutputting of the start-up energy from the auxiliary booster circuit 13and storage element 58 based on the control signal from the boostercircuit 12.

With the booster according to the eighteenth embodiment, all or a partof the boosted output is stored in the storage element (power storingunit) as energy for restarting the own operation and either one of thefirst start-up energy that is start-up energy output from the auxiliarybooster circuit and the second start-up energy that is start-up energyoutput from the storage element is output to the booster circuit.Accordingly, the start-up of the booster circuit can be performedreliably.

Although the storage element is used as an element for storing start-upenergy for restarting, a secondary cell or the like may also be used.Use of the secondary cell enables one to perform the start-up of thebooster circuit more reliably.

Nineteenth Embodiment

FIG. 29 is a diagram of a configuration of a booster according to anineteenth embodiment of the present invention. The booster has aconfiguration that additionally includes, in the configuration accordingto the thirteenth embodiment shown in FIG. 18, a voltage judging part 82a that controls timing in which the auxiliary booster circuit outputsbased on an output value (voltage) of an output of the auxiliary boostercircuit output to the booster circuit 12 and a switching part 83 a.Other configurations are the same as or equivalent to those of thethirteenth embodiment shown in FIG. 18 and the same reference numeralsdesignate those portions.

Referring to FIG. 29, the operation of this booster circuit isexplained. However, the feature that the booster circuit 12 performsboosting operation using either the start-up energy that is an output(auxiliary booster circuit output) of the auxiliary booster circuit 13or the operation energy that is a part of its own output fed back to thebooster circuit itself is the same as that in the other embodiments andexplanation is omitted.

The output from the auxiliary booster circuit 13 (i.e., output from theauxiliary booster circuit) is stored in a capacitor 86 in the voltagejudging part 82 a, and the stored voltage is compared in the comparatorcircuit 84 with a standard voltage value (V₀) generated by a constantvoltage element 85, such as a Zener diode. When the stored voltage ofthe capacitor 86 exceeds the standard voltage value (V₀), a switchingelement provided in the switching part 83 a, such as a MOSFET 87,becomes conducting to output the output of the auxiliary booster circuit(start-up energy) to the booster circuit 12. When the stored voltage ofthe capacitor 86 is not above the standard voltage value (V₀), theswitching element in the switching part 83 a is not conducting, so thatthe supply of the auxiliary booster circuit output to the boostercircuit 12 is suspended. The standard voltage (V₀) determined by thecapacitor 86 and the constant voltage element 85 may be advantageouslyadjusted to an optimum value, for example, in such a manner that whenthe energy stored in the capacitor in the last stage of the switchedcapacitor type circuit shown in FIG. 19 or the charged pump type circuitshown in FIG. 20 reaches a predetermined energy level that is sufficientfor starting up the booster circuit 12, the switching element, such asthe MOSFET 87, turns on.

When the amount of power generation by the power generating element 20is small, it may sometimes be the case that the output current that isoutput from the auxiliary booster circuit 13 is lower than the currentnecessary for starting up the booster circuit 12. In the circuitconfigurations of the boosters according to the first to the fifthembodiments, the current for starting up the booster circuit 12(start-up current) is insufficient. Accordingly, there is a possibilitythat the output voltage of the auxiliary booster circuit immediatelyafter the booster circuit 12 is started up instantaneously lowered,resulting in a failure to start up the booster circuit 12.

However, in the booster according to this embodiment, the standardvolume (V₀) is set so that the output of the auxiliary booster circuit13 is supplied to the booster circuit 12 when the amount of energy thatis stored in the capacitor 86 with a capacitance C_(x), E=(C_(x)V²)/2,reaches an amount of energy that allows start-up of the booster circuit12. Therefore, even when the amount of the power generation by the powergenerating element 20 is slight, a sufficient amount of start-up energyis stored with passage of time although a storage time in which theenergy is stored in the capacitor is longer. Accordingly, the start-upof the booster circuit 12 can be performed reliably.

When the power generating element 20 is a solar cell, a boosted outputcan be obtained at a lower luminance. In particular, with a solar cellarranged in the outdoor, luminance gradually increases from dawn, sothat the booster starts up automatically, and a boosted output can beobtained for a long time.

In the booster according to the nineteenth embodiment, the voltagejudging includes a comparator that compares the auxiliary boostercircuit output with a predetermined standard voltage and the switchingelement provided in the switching part is controlled based on the resultof comparison by the comparator. Accordingly, the start-up of thebooster circuit can be performed reliably independently of the powergeneration state of the power generating element.

Although the booster according to this embodiment includes, in thebooster according to the thirteenth embodiment shown in FIG. 18, thevoltage judging part 82 a and the switching part 83 a between theauxiliary booster circuit and the booster circuit, a configurationequivalent to this may be applied to the boosters according to thefourteenth and the fifteenth embodiments with similar effects as thoseof the booster according to the nineteenth embodiment.

Twentieth Embodiment

FIG. 30 is a diagram of a configuration of a booster according to atwentieth embodiment of the present invention. The booster depicted inFIG. 30 is configured in such a maimer that instead of the voltagejudging part 82 a and the switching part 83 a, a voltage judging part 82b and a switching part 83 b that have similar functions as those of thevoltage judging part 82 a and the switching part 83 a, respectively, areprovided. Other configurations are the same as or equivalent to those ofthe nineteenth embodiment shown in FIG. 29 and the same referencenumerals designate those portions.

Referring to FIG. 30, the operation of this booster circuit isexplained. However, the basic operation is the same as that in thenineteenth embodiment and explanation is omitted.

The voltage judging part 82 b includes a resistor, a capacitor 90,Darlington-connected transistors 91 and 92, and so on and when a storedvoltage that is stored in the capacitor in the last stage in theauxiliary booster circuit 13 exceeds V_(BE) (that is approximately equalto 1.2 V) of the Darlington-connected transistors 91 and 92, a switchingelement 93 in the switching part 83 b becomes conducting, so thatstart-up energy is supplied to the booster circuit 12. Although thevoltage judging part 82 b includes the Darlington-connected transistors91 and 92, the present invention is not limited to this connection and aconfiguration in which a resistor, a rectifier element and so on arecombined and a voltage drop that occurs in the rectifier element isutilized may also be used.

Also, in the booster according to the twentieth embodiment, by settingthe resistance values of the voltage judging part 82 b and the switchingpart 83 b to predetermined values, the booster can be operated in such amanner that when the energy amount E=(C₀V²)/2 reaches an energy amountthat allows start-up of the booster circuit 12, the output of theauxiliary booster circuit 13 is supplied to the booster circuit 12 inthe same manner as that in the booster according to the nineteenthembodiment. Accordingly, even when the power generation amount of thepower generating element 20 is slight, the start-up of the boostercircuit 12 can be performed reliably. The booster according to thetwentieth embodiment provides effects equivalent to those of the boosteraccording to the nineteenth embodiment but requires no comparator incontrast to the voltage judging part 82 a in the nineteenth embodiment.This provides advantages that power consumption reduces to improve theefficiency of energy storage in the storage element and cost decreases.

In the booster according to this embodiment, the voltage judging partincludes Darlington-connected transistors that become conducting whenthe auxiliary booster circuit output reaches a predetermined voltage andthe switching element provided in the switching part is controlled basedon the auxiliary booster circuit output and the voltage drop that occursbetween the base and emitter of the Darlington-connected transistors.Accordingly, the start-up of the booster can be performed reliablyindependently of the power generation state of the power generatingelement.

Although the booster according to the embodiment is configured toinclude the voltage judging part 82 b and the switching part 83 bbetween the auxiliary booster circuit and the booster circuit, aconfiguration equivalent to this may also be applied to the boostersaccording to the fourteenth to seventeenth embodiments with similareffects to those of the twentieth embodiment.

INDUSTRIAL APPLICABILITY

The booster according to the present invention is useful as a boosterfor use in a power source for mobile devices, and in particular, thebooster according to the present invention is suitable when an output ofa fuel cell or an output of a solar cell is used as an energy source.

1. A booster comprising: a booster circuit to which start-up energynecessary for starting up the booster circuit and operation energynecessary for continuing an operation of the booster circuit aresupplied, wherein the booster circuit generates a boosted outputobtained by boosting a low voltage generated by a power source, the lowvoltage output from the power source being a target to be boosted; and apower supply unit that is disposed independent of the power source andsupplies the start-up energy and the operation energy to the boostercircuit.
 2. The booster according to claim 1, wherein the low voltagethat is the target to be boosted is supplied from a solar cell.
 3. Thebooster according to claim 1, wherein the low voltage that is the targetto be boosted is supplied from a fuel cell.
 4. The booster according toclaim 1, wherein the power supply unit is a solar cell.
 5. The boosteraccording to claim 1, wherein the power supply unit is a lithium storagecell.
 6. The booster according to claim 1, wherein the power supply unitis a storage element that stores the boosted output and generates aconstant voltage output, and supplies the constant voltage output as thestart-up energy and the operation energy.
 7. A booster comprising: abooster circuit to which either one of start-up energy necessary forstarting up the booster circuit and operation energy necessary forcontinuing an operation of the booster circuit is supplied, wherein thebooster circuit generates a boosted output obtained by boosting anoutput voltage generated by a power source, the output voltage from thepower source being a target to be boosted; a power supply unit that isdisposed independent of the power source and supplies the start-upenergy; a selector circuit that outputs either one of the start-upenergy and the operation energy to the booster circuit, wherein thebooster circuit outputs all or a part of the boosted output to theselector circuit as the operation energy.
 8. The booster according toclaim 7, wherein the selector circuit comprises: a first rectifierelement connected between the power supply unit and the booster circuit;and a second rectifier element that is normally connected in a directionin which all or a part of the boosted output is fed back to the boostercircuit.
 9. The booster according to claim 7, further comprising: anoutput controller circuit that is provided in a stage subsequent to thebooster circuit and performs output control to the boosted outputobtained from the booster circuit.
 10. The booster according to claim 7,wherein the booster circuit comprises: a unit that controls an abilityof boosting of the booster based on the output control by the outputcontroller circuit.
 11. A booster comprising: a booster circuit to whichstart-up energy necessary for starting up the booster circuit andoperation energy necessary for continuing an operation of the boostercircuit are supplied, wherein the booster circuit generates a boostedoutput obtained by boosting a low voltage generated by a power source,the low voltage output from the power source being a target to beboosted; a power supplying unit that is disposed independent of thepower source and supplies the start-up energy; a switching unit that issupplied with the start-up energy from the power supplying unit andperforms output control of the start-up energy, wherein the boostercircuit feeds back all or a part of the boosted output to the boostercircuit as the operation energy and outputs the boosted output to theswitching unit as a supply stop signal for the start-up energy, and theswitching unit performs control whether to output the start-up energy tothe booster circuit based on a start-up signal, which is generated basedon power generation control of the input voltage as the target to beboosted and the supply stop signal.
 12. The booster according to claim11, wherein the switching unit comprises: a first switching element towhich the start-up signal is input; and a second switching element towhich the supply stop signal is input and connected to the firstswitching element in series, the switching unit causing the firstswitching element to be conducting when the start-up signal is ON whileinterrupting the first switching element when the start-up signal isOFF, and the switching unit causing the second switching element to beconducting when the start-up signal is ON while interrupting the secondswitching element when the start-up signal is OFF.
 13. A boostercomprising: a booster circuit to which either one of start-up energynecessary for starting up the booster circuit and operation energynecessary for continuing an operation of the booster circuit issupplied, wherein the booster circuit generates a boosted outputobtained by boosting a low voltage generated by a power source, the lowvoltage output from the power source being a target to be boosted; apower supplying unit that is disposed independent of the power sourceand supplies the start-up energy; a switching unit that is supplied withthe start-up energy from the power supplying unit and performs outputcontrol of the start-up energy; and a selector circuit that outputseither one of the start-up energy and the operation energy to thebooster circuit, wherein the booster circuit outputs all or a part ofthe boosted output to the selector circuit and the power supplying unit;the switching unit performs control whether to output the start-upenergy to the selector circuit based on a start-up signal, which isgenerated based on power generation control of the input voltage as thetarget to be boosted.
 14. The booster according to claim 13, furthercomprising: a rectifier element connected between the booster circuitand the power supplying unit in a forward direction.
 15. A boostercomprising: a booster circuit to which either one of start-up energynecessary for starting up the booster circuit and operation energynecessary for continuing an operation of the booster circuit issupplied, wherein the booster circuit generates a boosted outputobtained by boosting a low voltage generated by a power source, the lowvoltage output from the power source being a target to be boosted; apower supplying unit that is disposed independent of the power sourceand supplies the start-up energy; a switching unit that is supplied withthe start-up energy from the power supplying unit and performs outputcontrol of the start-up energy; a selector circuit that outputs eitherone of the start-up energy and the operation energy to the boostercircuit; and a signal delay circuit that generates a delay signalobtained by delaying a power generation request signal sent forgenerating the input voltage as the target to be boosted by apredetermined time and outputs the delay signal, wherein the boostercircuit outputs all or a part of the boosted output to the selectorcircuit and the power supplying unit, and the switching unit performscontrol whether to output the operation energy to the selector circuitbased on the delay signal.
 16. The booster according to claim 15,wherein the selector circuit comprises: a first rectifier elementconnected between the storage element and the booster circuit; and asecond rectifier element that is connected in a direction in which allor a part of the boosted output is fed back to the booster circuititself and in a forward direction.
 17. A booster comprising: a boostercircuit to which either one of start-up energy necessary for starting upthe booster circuit and operation energy necessary for continuing anoperation of the booster circuit is supplied, wherein the boostercircuit generates a boosted output obtained by boosting an input voltageas a target to be boosted; and an auxiliary booster circuit that outputsthe start-up energy generated based on the low voltage output to thebooster circuit, wherein the booster circuit feeds back all or a part ofthe boosted output to the booster circuit itself as the operationenergy.
 18. The booster according to claim 17, further comprising: aunit that controls start-up of the auxiliary booster circuit based onthe boosted output.
 19. The booster according to claim 18, furthercomprising: an output controller circuit provided around the boostercircuit and performing output control to the boosted output obtained bythe booster circuit.
 20. The booster according to claim 19, wherein theoutput controller circuit includes a constant voltage element.
 21. Thebooster according to claim 19, wherein the output controller circuitincludes a constant voltage element and a constant current element. 22.The booster according to claim 19, wherein the output control circuitcontrols boosting capability of the booster circuit.
 23. The boosteraccording to claim 19, wherein the output control circuit performs timeratio modulation control to the booster circuit.
 24. The boosteraccording to claim 17, further comprising: a power storing unit thatstores all or a part of the boosted output, wherein the booster circuitfeeds back a part of the boosted output to the booster circuit itself asthe operation energy and controls start-up of the auxiliary boostercircuit and the power storing unit based on the boosted output, and theselector circuit outputs to the booster circuit either one of thestart-up energy output from the auxiliary booster circuit and thestart-up energy output from the power storing unit.
 25. The boosteraccording to claim 24, wherein the selector circuit comprises: a firstrectifier element connected between the auxiliary booster circuit andthe booster circuit in a forward direction; and a second rectifierelement that is connected in a direction in which all or a part of theboosted output is fed back to the booster circuit and in a forwarddirection.
 26. The booster according to claim 24, wherein a rectifierelement is connected between the booster circuit and the power storingunit in a forward direction.
 27. The booster according to claim 17,further comprising: a voltage judging unit that judges an output voltageof an auxiliary booster circuit output that is an output of theauxiliary booster circuit; and a switching unit that switchessupply/stop of the auxiliary booster circuit output to the boostercircuit based on a result of judgment by the voltage judging unit. 28.The booster according to claim 27, wherein the voltage judging unitcomprises: a comparator that compares the auxiliary booster circuitoutput with a predetermined standard voltage, wherein a switchingelement included in the switching unit is controlled based on a resultof comparison by the comparator.
 29. The booster according to claim 27,wherein the voltage judging unit includes Darlington-connectedtransistors that become conducting when the auxiliary booster circuitoutput reaches a predetermined voltage, wherein a switching elementincluded in the switching unit is controlled based on the auxiliarybooster circuit output and a voltage drop that occurs between a base andan emitter of the Darlington-connected transistors.
 30. The boosteraccording to claim 17, wherein the auxiliary booster circuit includes aswitched capacitor type circuit.
 31. The booster according to claim 17,wherein the auxiliary booster circuit includes a charged pump typecircuit.